Orchid Biotechnology in Production and Improvement Rasika G
Total Page：16
File Type：pdf, Size：1020Kb
FEATURE Orchid Biotechnology in Production and Improvement Rasika G. Mudalige and Adelheid R. Kuehnle1 Department of Tropical Plant and Soil Sciences, University of Hawaii, 3190 Maile Way, Honolulu, HI 96822 The Orchidaceae is one of the largest full-length single copy clone, DOH1, which 2000b). DOMADS1 was expressed early in families of fl owering plants, with several was subsequently isolated from a Dendrobium the developing infl orescence and in all fl oral genera being used in cut fl ower and potted cDNA library of VSAM, shared considerable organ primordia. Its high expression in polli- plant production. The molecular biology of similarity to a class of homeobox genes naria suggested it could be an early regulator orchids, last reviewed in Kuehnle (1997), cov- known as class I knox (knotted-like) genes of pollen mother cell development. DOMADS ered research in phylogeny and systematics, (Yu et al., 2000). Northern analysis and in 2 was expressed early in the VSAM and in- fl oral physiology, and plant breeding. Only 10 situ hybridization revealed that DOH1/ovg2 creased in expression during the transition of orchid genes were cloned at that time. Since mRNA accumulated in all meristem-rich tis- the shoot apical meristem from the vegetative then, the total number of genes cloned from sues and its expression was down-regulated to reproductive phase, which might indicate a orchids has expanded considerably. The objec- at the beginning of fl oral transition (Yu and role in vegetative to reproductive phase change. tive of this paper is to: 1) provide an overview Goh, 2000a; Yu et al., 2000). A Dendrobium The expression pattern of DOMADS3, as re- of the function of some recently cloned genes; hybrid transformed with sense constructs of vealed by in situ hybridization, suggested that and 2) review advances made in other applica- DOH1 gene driven by the caulifl ower mosaic it might function as a regulatory factor in the tions of biotechnology in orchid production virus (CaMV) 35S promoter (Yu et al., 2000) formation of the TSAM and in the development and improvement. revealed that the overexpression of DOH1 of pedicel tissue. completely suppresses shoot organization Another transcription factor, ovg27, a ho- Functions of some cloned orchid genes and development. Anti-sense plants formed mologue of a Drosophila shuttle-craft gene, multiple shoot meristems and precociously was isolated from the VSAM of Dendrobium About 70 genes have been cloned from fl owered. With these results, the authors con- and appears to be important in maintaining seven orchid genera, namely Dendrobium, cluded that DOH1 is involved in controlling the vegetative state of shoot apical meristem Phalaenopsis, Doritaenopsis, Aranda, Brom- the formation and identity of the shoot apical in plants (Yu and Goh, 2000a). Also, a cDNA headia, Vanilla, and Cymbidium. These genes meristem, and thereby involved in maintaining clone, otg16, expressed only in the TSAM has can be divided into seven categories based on the basic plant architecture. shown signifi cant similarity to an Arabidopsis their presumptive functions (Table 1). Here Another fl oral homeotic gene was isolated casein kinase gene involved in protein phos- we review genes affecting fl ower induction, from red and white Phalaenopsis using Ampli- phorylation and signal transduction (Yu and fl ower color, fl ower senescence, and disease fi ed Fragment Length Polymorphism (Liu and Goh 2000a). The complete signal transduction resistance. Other genes have been cloned that Chen, 1999). A fragment that was differentially pathway in fl oral induction of orchids is yet affect primary metabolism, ovule development, amplifi ed, AM1-3, has shown 87% similarity to be discovered. cell division, and cell structure (Table 1). At to the fl oral homeotic gene AGL5 from Ara- Flower color (fl avonoid biosynthesis). The this time, the latter categories have had less bidopsis thaliana and 90% similarity to the biosynthesis of anthocyanins is well character- direct impact on commercial orchid production AG gene of Brassica napus at the deduced ized in many ornamental plants. The synthesis and improvement. amino acid sequence. AGL5 is known to act of fl avonoids, including anthocyanins, occurs Flower induction. The ability to time fl ow- downstream of AG in programming normal through the phenylpropanoid pathway, which ering for holidays and to hasten fl owering in carpel and ovule development. starts with the stepwise condensation of three otherwise slow-maturing orchids is of keen MADS box genes. MADS-box genes com- acetate units from malonyl-coA with 4-cou- interest to growers of commercially cropped prise another important family of transcription maroyl CoA to yield tetrahydroxychalcone orchids. Several research groups are examin- factors that regulate the transition of meristem (Heller and Forkmann, 1988). This reaction ing the genetic aspects of fl ower induction and identity. They are characterized by the presence is catalyzed by the enzyme chalcone synthase the transition of the apical meristem from a of a highly conserved DNA binding domain (CHS), which is attractive to researchers for vegetative shoot apical meristem (VSAM) (MADS-box) and a second conserved domain fl ower color manipulation. The magnifi cent through a transitional shoot apical meristem (K-box) involved in protein-protein interac- spectrum of colors found in orchids is mainly (TSAM) to a reproductive meristem. Specifi - tions. The fi rst fl ower-specifi c MADS-box gene due to the accumulation of anthocyanins in their cally, several orchid genes have been identi- from an orchid was isolated from the mature fl owers (Arditti and Fisch, 1977). Although ca- fi ed to be so-called homeobox and MADS box fl ower cDNA library of an orchid hybrid rotenoids and chlorophylls contribute to fl ower genes, which encode transcription factors and Aranda Deborah using an agamous cDNA from color in many orchids, there are no detailed are preferentially expressed in vegetative or Arabidopsis as the probe (Lu et al., 1993). A reports of cloned orchid genes associated with transitional stages (Table 1). single clone, om1 was isolated, with an open the biosynthesis of these compounds except Homeobox genes. Five clones were identi- reading frame (ORF) of 750 base pairs (bp) for a brief mention of an amplifi ed restriction fi ed by mRNA differential display as transcrip- encoding a polypeptide of 250 amino acids. fragment of Phalaenopsis, AM4-1, which tion factors involved in fl oral induction (Yu and Expression of om1 was limited to the petals showed similarity to the geranyl-geranyl pyro- Goh, 2000a). Of these, the partial cDNA clone and sepals of mature fl owers but was not found phosphate synthase gene (Liu and Chen, 1999). ovg2 showed signifi cant similarity to homeo- in the column, early infl orescence, or fl oral Genes for other important enzymes cloned in box genes, which are a universal group of tran- buds, suggesting that om1 might be playing an orchids are fl avanone 3-hydroxylase (F3H) and scription factors important in development. The important role in petal development. dihydrofl avonol 4-reductase (DFR). Another orchid MADS-box gene, otg7, Chalcone synthase genes. The earliest re- Received for publication 31 July 2001. Accepted for expressed only in the TSAM was identifi ed port of the isolation of fl ower color genes in publication 31 Jan. 2003. This paper is based on the from Dendrobium (Yu and Goh, 2000a). orchids appeared as an abstract only by Yong invited presentation at the 98th American Society Clone otg7 was used later to isolate three new and Chua (1990), in which four cDNA clones of Horticultural Science Annual Conference, Orchid Symposium, Sacramento, Calif. MADS box genes, DOMADS1, DOMADS2, encoding CHS were isolated from a cDNA 1To whom reprint requests should be addressed. and DOMADS3, all of which were expressed library of a Dendrobium hybrid. These DNA E-mail address: [email protected]. exclusively in fl oral tissues (Yu and Goh, sequences are absent in all the searchable HORTSCIENCE, VOL. 39(1), FEBRUARY 2004 11 3-7396, p11-17 11 2/17/04, 10:03:16 AM FEATURE Table 1. Isolated orchid genes or cDNA clones and their presumptive function. Gene or cDNA Orchid Presumptive Referencez and designation genus function (GenBank accession numbers) Flower Induction ovg2/DOH1 Dendrobium Homeobox gene, class 1 knox gene Yu and Goh, 2000a; Yu et al., 2000 (AF100326, AJ276389) om1 ×Aranda Flower specifi c MADS box gene Lu et al., 1993. (X69107) otg7 Dendrobium MADS box gene Yu and Goh, 2000a. (AF107588) DOMADS1, 2 and 3 Dendrobium MADS-box genes in AP1/AGL9 subfamily Yu and Goh, 2000b. (AF198174-b) ovg27 Dendrobium Transcriptional repressor Yu and Goh, 2000a. (AF100331) otg 16 Dendrobium Casein kinase1, a homologue of serine/threonine Yu and Goh, 2000a. (AF107592) protein kinase. Cell Division and Cell Structure Ovg14 Dendrobium Transcriptional regulator of cell cycle regulators. Yu and Goh, 2000a. (AF100328) otg4 Dendrobium Cell division control protein, a homologue of yeast NDA4 Yu and Goh, 2000a. (AF107586) Ovg30 Dendrobium DNA binding protein, regulate cell cycle progression Yu and Goh, 2000a. (AF100333) Ovg29 Dendrobium Putative 21D7 protein. Degradation of cell cycle Yu and Goh, 2000a. (AF100332) regulatory proteins otg2 Dendrobium Myosin heavy chain Yu and Goh 2000a. (AF107585) P-ACT1 Phalaenopsis Actin partial clone Nadeau et al., 1996. (U18102) ACT2 Phalaenopsis Actin-like protein Huang et al., 2000. (AF246715) --- Phalaenopsis Profi lin, an actin binding protein Lee et al., 1999b. (AF126263) Flower Senescence Ds-ACS1, Ds-ACS2 ×Doritaenopsis ACC synthase OʼNeill et al., 1993 (L07882, L07883) ACS2, ACS3 ACC synthase Bui and OʼNeill, 1998 (AF007213, AF00721) pOACS10 Phalaenopsis ACC synthase Do and Huang, 1998. (Z77854) --- ×Doritaenopsis ACC oxidase Nadeau et al., 1993. (L07912) --- ×Doritaenopsis ACC oxidase Nadeau and OʼNeill, 1995 (L37103) pPEFEA Phalaenopsis ACC oxidase Lee and Huang, 1995 Petr1 Phalaenopsis Homologue of ethylene receptor Do et al., 1999.