DOCSLIB.ORG

AXR1 Acts After Lateral Bud Formation to Inhibit Lateral Bud Growth in Arabidopsis

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
AXR1 Acts After Lateral Bud Formation to Inhibit Lateral Bud Growth in Arabidopsis This is a repository copy of AXR1 acts after lateral bud formation to inhibit lateral bud growth in Arabidopsis. White Rose Research Online URL for this paper: https://eprints.whiterose.ac.uk/262/ Article: Stirnberg, P., Leyser, O. and Chatfield, S.P. (1999) AXR1 acts after lateral bud formation to inhibit lateral bud growth in Arabidopsis. Plant Physiology. pp. 839-847. ISSN 0032-0889 Reuse Items deposited in White Rose Research Online are protected by copyright, with all rights reserved unless indicated otherwise. They may be downloaded and/or printed for private study, or other acts as permitted by national copyright laws. The publisher or other rights holders may allow further reproduction and re-use of the full text version. This is indicated by the licence information on the White Rose Research Online record for the item. Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing [email protected] including the URL of the record and the reason for the withdrawal request. [email protected] https://eprints.whiterose.ac.uk/ Plant Physiology, November 1999, Vol. 121, pp. 839–847, www.plantphysiol.org © 1999 American Society of Plant Physiologists AXR1 Acts after Lateral Bud Formation to Inhibit Lateral Bud Growth in Arabidopsis1 Petra Stirnberg, Steven P. Chatfield, and H.M. Ottoline Leyser* Department of Biology, University of York, P.O. Box 373, York YO10 5YW, United Kingdom Several mutants with altered auxin sensitivity have been The AXR1 gene of Arabidopsis is required for many auxin re- produced in Arabidopsis. One such locus, AXR1, is defined sponses. The highly branched shoot phenotype of mature axr1 by an allelic series of recessive mutations. The phenotype mutant plants has been taken as genetic evidence for a role of auxin of axr1 mutant plants is pleiotropic, with defects in root, in the control of shoot branching. We compared the development of hypocotyl, stamen, and stem elongation, vascular develop- lateral shoots in wild-type Columbia and axr1-12 plants. In the wild ment, lateral root formation, and root gravitropism. Leaf type, the pattern of lateral shoot development depends on the morphology is altered and shoot branching is increased at developmental stage of the plant. During prolonged vegetative maturity (Estelle and Somerville, 1987; Lincoln et al., 1990). growth, axillary shoots arise and develop in a basal-apical sequence. All axr1 tissues examined showed reduced auxin sensitiv- After floral transition, axillary shoots arise rapidly along the primary shoot axis and grow out to form lateral inflorescences in an apical- ity in a variety of assays, including rapid gene induction by basal sequence. For both patterns, the axr1 mutation does not affect auxin (Abel et al., 1995; Timpte et al., 1995). This suggests the timing of axillary meristem formation; however, subsequent that the AXR1 protein is required for auxin signaling. The lateral shoot development proceeds more rapidly in axr1 plants. The AXR1 gene encodes a protein related to the amino-terminal outgrowth of lateral inflorescences from excised cauline nodes of half of ubiquitin-activating enzyme; sequencing of severe wild-type plants is inhibited by apical auxin. axr1-12 nodes are mutant alleles such as axr1-12 indicates complete loss of resistant to this inhibition. These results provide evidence for com- protein function (Leyser et al., 1993). mon control of axillary growth in both patterns, and suggest a role Although these mutant and transgenic lines suggest that for auxin during the late stages of axillary shoot development branching is regulated by auxin in vivo, they were only following the formation of the axillary bud and several axillary leaf investigated at a cursory level. Altered branching may be primordia. an indirect consequence of other auxin-regulated pheno- types. axr1-12 plants produce more branches than the wild type, and are less fertile (Lincoln et al., 1990). There is In plants, the shoot apex has an inhibitory effect on the evidence that developing fruits limit lateral branching (Ta- development of lateral shoots. The theory that the plant mas et al., 1979; Hensel et al., 1994). Therefore, the in- hormone auxin (indole-3-acetic acid [IAA]) is a signal in creased branching in mature axr1 plants may be a conse- this apical dominance remains a matter of debate. This quence of their infertility. theory is based on the effects of auxin application on de- The in vivo role of auxin is further called into question by capitated plants and the discovery of basipetal auxin trans- examining the pattern of lateral shoot development in Ara- port. The mechanism by which auxin acts is still obscure bidopsis. If apically derived auxin acts as an inhibitor of and is likely to be indirect (see Phillips, 1975; Trewavas, axillary branching, one might expect the lateral buds clos- 1981; Cline, 1991, 1994). est to the shoot apex to be the most repressed, giving a The increasing number of mutations or transgenes that basal-apical (acropetal) sequence of bud growth. Arabidop- affect auxin content, transport, or sensitivity, especially in sis shows this pattern during prolonged vegetative growth, Arabidopsis, provides a different approach to investigate e.g. in late-flowering ecotypes (Grbic´and Bleecker, 1996). the role of auxin in apical dominance, and in particular However, lateral inflorescences develop in an apical-basal which stages of lateral shoot development it regulates in (basipetal) sequence after floral transition (Alvarez et al., vivo. Plants expressing the IAA biosynthetic genes from 1992; Hempel and Feldman, 1994). Agrobacterium tumefaciens have high endogenous IAA lev- To further assess the role of auxin in the regulation of els and increased apical dominance (Klee et al., 1987; Ro- Arabidopsis shoot branching, we compared axillary shoot mano et al., 1993, 1995). The iaaL gene from Pseudomonas development in the wild type and axr1-12 to determine the savastanoi, encoding an enzyme that conjugates IAA to Lys, earliest stage when differences can be detected. In addition, has been transformed into tobacco, resulting in reduced we compared the auxin sensitivity of wild-type and axr1-12 levels of free IAA and reduced apical dominance (Romano lateral inflorescence outgrowth using nodes excised from et al., 1991). the primary inflorescence. The axr1-12 mutation does not affect early stages of axillary shoot development; however, 1 This work was supported by a grant from the Biotechnology it promotes the subsequent growth of axillary shoots initi- and Biological Sciences Research Council of the United Kingdom. ated by the acropetal and basipetal pattern. It also renders * Corresponding author; e-mail [email protected]; fax the outgrowth of isolated lateral inflorescences resistant to 44–1904–434312. auxin inhibition. These results suggest a role for auxin in 839 840 Stirnberg et al. Plant Physiol. Vol. 121, 1999 the stages of lateral shoot development following axillary node with a visible axillary bud between parts of the apical meristem formation. and the basal internode and 8 to 15 mm long were excised from elongating primary inflorescences. The length of the bud was measured and the node was placed over the gap MATERIALS AND METHODS of a split plate, with the apical end inserted into one agar Plants for Morphometric and Histological Analyses half and the basal end into the other. Plates containing up to three excised nodes were incubated in the conditions Seeds of Arabidopsis (wild type and axr1-12, ecotype described above in near-vertical orientation. The lengths of Columbia) were sown onto F2 compost (Levington Horti- the axillary shoots were measured daily with a metric ruler culture, Ipswich, UK) in shallow trays consisting of indi- until d 8 following excision. Lengths were determined from ϫ vidual 4- 4-cm pots (P40, Cookson Plantpak, Maldon, the point where the adaxial side of the subtending petiole UK), with several seeds per pot. Compost for short-day- inserted into the stem to the tip of the axillary leaves when grown plants was treated with systemic insecticide (Inter- the bud was still closed, or to the inflorescence apex when cept 70WG, Levington Horticulture) before sowing. After 2 the branch had started elongating. to5dofcold treatment at 4°C, trays were transferred to 21°C, 8-h (short) or 16-h (long) photoperiods and watered Ϫ with tap water. Light intensities were 130 and 50 ␮mol m 2 Ϫ RESULTS s 1 for the short and long photoperiod, respectively. Seed- lings were thinned out to one per pot after germination. Development of the Branched Inflorescence in Long Photoperiods Histology To establish when differences in branching between axr1-12 and wild-type plants first arise, the development of Tissue was fixed overnight in 3% (v/v) formaldehyde/ their shoot systems was studied over time. Neither wild- 1.25% (v/v) glutaraldehyde in 0.05 m sodium phosphate type nor axr1-12 rosettes showed visible axillary buds or buffer (pH 7.0), dehydrated in a graded ethanol series, branches during vegetative growth in long photoperiods. transferred to Histoclear (National Diagnostics, Atlanta), After the transition to reproductive growth, flower buds and embedded in Paraplast Plus (Sigma-Aldrich, Poole, became visible in the center of the rosettes and the plants UK). Microtome sections (8 ␮m) were affixed to glass mi- started to bolt, as defined by visible elongation of the croscope slides covered with adhesive (1% [w/v] gelatin, lowermost internode of the primary inflorescence. The date 13% [v/v] glycerol), dewaxed in xylene, rehydrated in an of bolting was noted for each individual plant. Samples of ethanol series, stained in 0.025% (w/v) aqueous toluidine five to eight plants of each genotype were removed and blue, dehydrated in an ethanol series followed by xylene, subjected to morphometric analysis covering a time course and coverslips were mounted with DPX (BDH Laboratory of 3-d intervals between 3 and 18 d after bolting.
Load more

Recommended publications
  • The Control of Shoot Branching: an Example of Plant Information Processing
    Plant, Cell and Environment (2009) 32, 694–703 doi: 10.1111/j.1365-3040.2009.01930.x The control of shoot branching: an example of plant information processing OTTOLINE LEYSER Department of Biology, Area 11, University of York, York YO10 5YW, UK ABSTRACT the apical–basal axis defined by the establishment of the shoot apical meristem at one end, and the root apical mer- Throughout their life cycle, plants adjust their body plan istem at the other. Post-embryonically, the meristems give to suit the environmental conditions in which they are rise to the entire shoot and root systems, respectively. Fur- growing. A good example of this is in the regulation of thermore, the tissues they establish can produce secondary shoot branching. Axillary meristems laid down in each leaf meristems, which if activated can produce entirely new formed from the primary shoot apical meristem can remain axes of growth with the same developmental potential as dormant, or activate to produce a branch. The decision the primary root or shoot from which they were derived. whether to activate an axillary meristem involves the assess- Thus, the body plan of a plant is determined continuously ment of a wide range of external environmental, internal throughout its life cycle, allowing it to be exquisitely envi- physiological and developmental factors. Much of this infor- ronmentally responsive. Plants can alter their body plan to mation is conveyed to the axillary meristem via a network suit their environment, and thus the environmentally regu- of interacting hormonal signals that can integrate inputs lated development of new growth axes is functionally from diverse sources, combining multiple local signals to equivalent to environmentally regulated animal behav- generate a rich source of systemically transmitted informa- iours.
    [Show full text]
  • Specification and Maintenance of the Floral Meristem: Interactions Between Positively- Acting Promoters of Flowering and Negative Regulators
    SPECIAL SECTION: EMBRYOLOGY OF FLOWERING PLANTS Specification and maintenance of the floral meristem: interactions between positively- acting promoters of flowering and negative regulators Usha Vijayraghavan1,*, Kalika Prasad1 and Elliot Meyerowitz2,* 1Department of MCB, Indian Institute of Science, Bangalore 560 012, India 2Division of Biology 156–29, California Institute of Technology, Pasadena, CA 91125, USA meristems that give rise to modified leaves – whorls of A combination of environmental factors and endoge- nous cues trigger floral meristem initiation on the sterile organs (sepals and petals) and reproductive organs flanks of the shoot meristem. A plethora of regulatory (stamens and carpels). In this review we focus on mecha- genes have been implicated in this process. They func- nisms by which interactions between positive and nega- tion either as activators or as repressors of floral ini- tive regulators together pattern floral meristems in the tiation. This review describes the mode of their action model eudicot species A. thaliana. in a regulatory network that ensures the correct temporal and spatial control of floral meristem specification, its maintenance and determinate development. Maintenance of the shoot apical meristem and transitions in lateral meristem fate Keywords: Arabidopsis thaliana, floral activators, flo- ral mesitem specification, floral repressors. The maintenance of stem cells is brought about, at least in part, by a regulatory feedback loop between the ho- THE angiosperm embryo has a well established apical- meodomain transcription factor WUSCHEL (WUS) and basal/polar axis defined by the positions of the root and genes of the CLAVATA (CLV) signaling pathway2. WUS shoot meristems. Besides this, a basic radial pattern is is expressed in the organizing centre and confers a stem also established during embryogenesis.
    [Show full text]
  • Inhibition of Lateral Shoot Formation by RNA Interference and Chemically Induced Mutations to Genes Expressed in the Axillary Meristem of Nicotiana Tabacum L
    Hamano et al. BMC Plant Biol (2021) 21:236 https://doi.org/10.1186/s12870-021-03008-3 RESEARCH ARTICLE Open Access Inhibition of lateral shoot formation by RNA interference and chemically induced mutations to genes expressed in the axillary meristem of Nicotiana tabacum L. Kaori Hamano* , Seiki Sato, Masao Arai, Yuta Negishi, Takashi Nakamura, Tomoyuki Komatsu, Tsuyoshi Naragino and Shoichi Suzuki Abstract Background: Lateral branches vigorously proliferate in tobacco after the topping of the inforescence portions of stems for the maturation of the leaves to be harvested. Therefore, tobacco varieties with inhibited lateral shoot forma- tion are highly desired by tobacco farmers. Results: Genetic inhibition of lateral shoot formation was attempted in tobacco. Two groups of genes were exam- ined by RNA interference. The frst group comprised homologs of the genes mediating lateral shoot formation in other plants, whereas the second group included genes highly expressed in axillary bud primordial stages. Although “primary” lateral shoots that grew after the plants were topped of when fower buds emerged were unafected, the growth of “secondary” lateral shoots, which were detected on the abaxial side of the primary lateral shoot base, was signifcantly suppressed in the knock-down lines of NtLs, NtBl1, NtREV, VE7, and VE12. Chemically induced mutations to NtLs, NtBl1, and NtREV similarly inhibited the development of secondary and “tertiary” lateral shoots, but not primary lateral shoots. The mutations to NtLs and NtBl1 were incorporated into an elite variety by backcrossing. The agronomic characteristics of the backcross lines were examined in feld trials conducted in commercial tobacco production regions. The lines were generally suitable for tobacco leaf production and may be useful as new tobacco varieties.
    [Show full text]
  • The American Woods
    TH E I A N W O O D S A M E R C , EXHIB ITED BY ACTUAL SPECIMENS AND WITH C PIO EXPLANAT RY TEXT O US O , ROM E Y N B H H B A OU G . , . RT IX PA . REPRES ENTI NG TWENTY - FIVE S PEC I ES TWENTY - F I VE S ETS OF S E TI O NS C . LOWVI L LE N Y . U A . s . , , . P U B LI SHED AN D SEC TI O NS PREPARED B Y THE AU THOR . Copy rig ht ninet B Y R O M E WE ED—P RSONS PRI NTING A CC . E L E C TR O TY P E R S A N D P R I N TE R S ALB ANY , N . Y . T O mcfl Q i nzhnt m . i ff 1 Qé ? , P M N F TU S . AR O G FORESTER U . DE T E T UL , A RIC RE , T I X A M E R I C A N W O O D P A R , S , DEDI ATED AS AN EXPRESSION OF HIGHE TE TEE IS C S S M. 743130 EF E T THE ERIE PR AC O S S. The necessity of more generally diffu sed information concerning the variety and importance of ou r forest trees is j u stifi c ati on enou gh for the n w n n appeara ce of this work, especially at this day, he the dema ds of n Forestry in this cou ntry are constantly more and more kee ly felt .
    [Show full text]
  • Patterns of Floral Bud Development in Canes of Erect and Trailing Blackberries
    J. AMER. SOC. HORT. SCI. 128(1):3–7. 2003. Patterns of Floral Bud Development in Canes of Erect and Trailing Blackberries Fumiomi Takeda1 U.S. Department of Agriculture, Agricultural Research Service, Appalachian Fruit Research Station, 45 Wiltshire Road, Kearneysville, WV 25430 Bernadine C. Strik and Derek Peacock2 Department of Horticulture, 4017 Agriculture and Life Science Building, Oregon State University, Corvallis, OR 97331 John R. Clark Department of Horticulture, 316 Plant Science Building, University of Arkansas, Fayetteville, AR 72701 ADDITIONAL INDEX WORDS. floral primordia, floricane, inflorescence, microscopy, Rubus ABSTRACT. Flower bud development was studied in ‘Cherokee’, ‘Boysen’, and ‘Marion’ blackberries (Rubus subgenus Rubus Watson). In ‘Cherokee’ (erect type), the transition to reproductive development in buds on the branch canes occurred during September in Arkansas and Oregon. Transitions of buds in the axils of the most basal nodes (proximal to the main cane) and the most distal nodes lagged behind buds in the midsection (about nodes 6 to 10). Along the midsection of branch canes, the buds developed uniformly. In buds of ‘Boysen’ and ‘Marion’ (trailing type), the transition to reproductive development occurred in October and sepal primordia were observed in most buds examined by November. Progression of floral bud development continued into January, but at a slower rate than in autumn. Buds on the main canes (>3 m long) of ‘Boysen’ and ‘Marion’ remained at a more advanced stage of flower bud differentiation than buds on the basal branch canes. In both cultivars, buds from the middle one-third section, and sometimes buds from the bottom one-third section, tended to be more advanced than those buds in the top one-third section during much of the sampling period.
    [Show full text]
  • Axillary Bud Banks of Two Semiarid Perennial Grasses: Occurrence, Longevity, and Contribution to Population Persistence
    Oecologia (1997) 110:584±591 Ó Springer-Verlag 1997 J.R. Hendrickson á D.D. Briske Axillary bud banks of two semiarid perennial grasses: occurrence, longevity, and contribution to population persistence Received: 12 August 1996 / Accepted: 30 December 1996 Abstract The occurrence, longevity, and contribution of modifying population structure of these two species. Bud axillary bud banks to population maintenance were number per square meter for B. curtipendula was 25% investigated in a late-seral perennial grass, Bouteloua lower in the long-term grazed compared to the long-term curtipendula, and a mid-seral perennial grass, Hilaria ungrazed community based on a reduction in both tiller belangeri, in a semiarid oak-juniper savanna. Axillary number per plant and plant number per square meter. In buds of both species were evaluated over a 2-year period contrast, bud number per square meter for H. belangeri in communities with contrasting histories of grazing by was 190% greater in the long-term grazed than in the domestic herbivores. A double staining procedure uti- long-term ungrazed community based on a large increase lizing triphenyl tetrazolium chloride and Evan's blue in plant density per square meter. Minimal contributions indicated that both viable and dormant axillary buds of axillary bud banks to annual maintenance of tiller remained attached to the base of reproductive parental populations in this mid- and late-seral species under- tillers for 18±24 months which exceeded parental tiller scores the ecological importance of consistent tiller re- longevity by approximately 12 months. Bud longevity of cruitment from recently developed axillary buds.
    [Show full text]
  • Apical Dominance in Alstroemeria Cultured in Vitro
    Apical Dominance in Alstroemeria Cultured In Vitro P. Pumisutapon, R.G.F. Visser and G.-J. De Klerk Wageningen UR Plant Breeding PO Box 16, 6700 AA, Wageningen The Netherlands Keywords: axillary buds, rhizomes, bud outgrowth, decapitation, auxin Abstract Apical dominance in Alstroemeria is studied to develop an improved propagation protocol for this crop. Four types of explants were prepared: an intact rhizome with two intact shoots (+R+2S), an intact rhizome with two decapitated shoots (+R-2S), a decapitated rhizome with two intact shoots (-R+2S), and a decapitated rhizome with two decapitated shoots (-R-2S). The explants were cultivated on solid MS medium with 9 µM 6-benzylaminopurine (BAP). -R-2S explants showed the highest and +R+2S the lowest axillary-bud outgrowth. Outgrowth in -R+2S and +R-2S explants was intermediate. So, axillary buds are released by removal of the rhizome tip and by removal of the shoot tips. In both decapitated shoots and decapitated rhizomes, application of lanolin with 3- indolebutyric acid (IBA) to the cut end restored apical dominance. This indicates that both tips exert an effect via basipetally transported auxin. INTRODUCTION Alstroemeria plants consist of aerial shoots and a rhizome. Growth occurs sympodially: at each node, the apex of the horizontally growing rhizome changes direction of growth from horizontal to vertical, forms a shoot, and then stops growing. At the same time, the first axillary bud at the node grows out horizontally and continues as rhizome. Thus, the rhizome is composed of segments of axillary shoots. The second (next higher) axillary bud in a shoot may stay dormant or may develop into a lateral rhizome (Van Schaik, 1998).
    [Show full text]
  • Identifying Plant Tissues
    + Identifying Plant Tissues Chapter 4 + Combining Cells to Form Tissues ! Plants grow as cells divide to produce new cells in areas of the plant called meristems. ! After new cells are produced, they specialize for certain functions, enlarging and changing their structure to match their function. ! Cells…..tissues…..tissue systems…..organs + Four Main Types of Tissue Systems ! Meristematic tissue system- contains cells that are actively dividing to produce new plant tissue ! Ground tissue system- contains tissues that make up the bulk of the plant ! Do photosynthesis ! Support ! Store food ! Repair damage + Four Types of Tissue Systems ! Vascular tissue system- conducts water, minerals, and sugars throughout plant ! Dermal tissue system- protect plant and prevents water loss from tissues + Meristematic Tissues ! Meristematic tissues are tissues where cells are actively multiplying to provide new cells for plant growth. ! permanent regions of active cell division ! all purpose cells ! can become any type of plant cell ! small, box-shaped, small vacuoles + Meristematic Tissues ! As the cells enlarge, they begin to differentiate, becoming specialized for a certain function. ! Two plant organ systems- ! Shoot system- above ground, supports leaves, flower, and fruits ! Root system- underground, absorbs water and minerals + Meristematic Tissues ! Four types of meristems ! Apical meristems ! Axillary buds ! Lateral meristems ! Intercalary meristems + Meristematic Tissue - Apical ! Apical Meristems - Found at the tips of roots and shoots. Plants get taller, and roots get longer, from their tips. ! Increase in length as the apical meristems produce new cells (primary growth) ! Divide to produce new cells, which elongate, making roots get longer and shoots get taller. ! Primary Meristems ! Protoderm ! Ground Meristem ! Procambium + Meristematic Tissue – Apical ! Once cells elongate and differentiate into a particular cell type, they usually can’t divide any more due to their rigid cell walls.
    [Show full text]
  • Molecular Mechanism of Lateral Bud Differentiation of Pinus Massoniana
    www.nature.com/scientificreports OPEN Molecular mechanism of lateral bud diferentiation of Pinus massoniana based on high‑throughput sequencing Hu Chen1,2,3,4, Jianhui Tan1,3, Xingxing Liang1, Shengsen Tang1,2, Jie Jia1,3,4 & Zhangqi Yang1,2,3,4* Knot‑free timber cultivation is an important goal of forest breeding, and lateral shoots afect yield and stem shape of tree. The purpose of this study was to analyze the molecular mechanism of lateral bud development by removing the apical dominance of Pinus massoniana young seedlings through transcriptome sequencing and identify key genes involved in lateral bud development. We analyzed hormone contents and transcriptome data for removal of apical dominant of lateral buds as well as apical and lateral buds of normal development ones. Data were analyzed using an comprehensive approach of pathway‑ and gene‑set enrichment analysis, Mapman visualization tool, and gene expression analysis. Our results showed that the contents of auxin (IAA), Zea and strigolactone (SL) in lateral buds signifcantly increased after removal of apical dominance, while abscisic acid (ABA) decreased. Gibberellin (GA) metabolism, cytokinin (CK), jasmonic acid, zeatin pathway‑related genes positively regulated lateral bud development, ABA metabolism‑related genes basically negatively regulated lateral bud diferentiation, auxin, ethylene, SLs were positive and negative regulation, while only A small number of genes of SA and BRASSINOSTEROID, such as TGA and TCH4, were involved in lateral bud development. In addition, it was speculated that transcription factors such as WRKY, TCP, MYB, HSP, AuxIAA, and AP2 played important roles in the development of lateral buds. In summary, our results provided a better understanding of lateral bud diferentiation and lateral shoot formation of P.
    [Show full text]
  • Opposing Influences of TAC1 and LAZY1 on Lateral Shoot Orientation
    www.nature.com/scientificreports OPEN Opposing infuences of TAC1 and LAZY1 on Lateral Shoot Orientation in Arabidopsis Courtney A. Hollender1*, Joseph L. Hill Jr. 1, Jessica Waite2,3 & Chris Dardick2 TAC1 and LAZY1 are members of a gene family that regulates lateral shoot orientation in plants. TAC1 promotes outward orientations in response to light, while LAZY1 promotes upward shoot orientations in response to gravity via altered auxin transport. We performed genetic, molecular, and biochemical assays to investigate possible interactions between these genes. In Arabidopsis they were expressed in similar tissues and double mutants revealed the wide-angled lazy1 branch phenotype, indicating it is epistatic to the tac1 shoot phenotype. Surprisingly, the lack of TAC1 did not infuence gravitropic shoot curvature responses. Combined, these results suggest TAC1 might negatively regulate LAZY1 to promote outward shoot orientations. However, additional results revealed that TAC1- and LAZY1 infuence on shoot orientation is more complex than a simple direct negative regulatory pathway. Transcriptomes of Arabidopsis tac1 and lazy1 mutants compared to wild type under normal and gravistimulated conditions revealed few overlapping diferentially expressed genes. Overexpression of each gene did not result in major branch angle diferences. Shoot tip hormone levels were similar between tac1, lazy1, and Col, apart from exceptionally elevated levels of salicylic acid in lazy1. The data presented here provide a foundation for future study of TAC1 and LAZY1 regulation of shoot architecture. Lateral organ orientation in both shoots and roots plays a key role in a plant’s interaction with the environ- ment and its ability to access resources such as light and water.
    [Show full text]
  • Leaf Blades on Magnolia Floral Buds
    Leaf blades on magnolia floral buds by John D. Freeman and floral buds are entirely enclosed and protected by a pair of leaf parts, Occasional development of a leaf the stipules, which may be much larger blade near the apex of a Magnolia in the case of floral buds than in either flower bud has probably been observed typical Magnolia leaves or vegetative by many who collect, study, and grow buds. Paired stipules are sometimes these plants. Discovery of an example apparently fused into one unit (as in of this anomaly on a branch of t)f. Magnolia) or may be present as macrophylla collected by Harold separate valve-like structures (as in Hopkins and me at Oak Hill, AL, in Liriodendron). Since the outermost May 1985 (see photographs) led to flower parts are enclosed by stipules in development of this note at his Magnolia buds, the outer perianth suggestion. segments are not primarily protective. The botanical nature of the When little distinction exists among structure(s) enclosing Magnolia buds, perianth segments except the relative both vegetative and floral, is somewhat positions, they are typically called unusual. In most plants the scales tepals rather than sepals and petals. covering vegetative buds represent Abscission scars from stipules produce leaves that are reduced in size and the rings that encircle young twigs in specialized to protect bud contents, but members of Magnoliaceae. If one not in Magnolia. The outer portions of tends to think of bud scales of floral buds in most species consist of Magnolia in terms of function instead perianth segments (actual flower parts) of origin, this can lead to the erroneous known as sepals, but not in Magnolia.
    [Show full text]
  • The Effect of Hormones and Chemical Growth Regulators on Ear Development and Grain Yield of Nonprolific Corn (Zea Mays L.) Gholamreza Khosravi Iowa State University
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1980 The effect of hormones and chemical growth regulators on ear development and grain yield of nonprolific corn (Zea mays L.) Gholamreza Khosravi Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Agricultural Science Commons, Agriculture Commons, and the Agronomy and Crop Sciences Commons Recommended Citation Khosravi, Gholamreza, "The effect of hormones and chemical growth regulators on ear development and grain yield of nonprolific corn (Zea mays L.) " (1980). Retrospective Theses and Dissertations. 6698. https://lib.dr.iastate.edu/rtd/6698 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS This was produced from a copy of a document sent to us for microfilming. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the material submitted. The following explanation of techniques is provided to help you understand markings or notations which may appear on this reproduction. 1. The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting through an image and duplicating adjacent pages to assure you of complete continuity.
    [Show full text]