Female and Hermaphrodite Flowers on a Chimeric Gynomonoecious

crossing among these lines to create F 1994. Enrichment of microsatellites from the citrus ge- both types of flowers (Baker 1966; Brock- 2 nome using biotinylated oligonucleotide sequences progeny [the progeny design employed by bound to streptavidin-coated magnetic particles. man and Bocquet 1978; Burrows 1960; Dul- Arens et al. (1995)]. For H. acuminata, this BioTechniques 16:657–662. berger and Horovitz 1984; Horovitz and design would take at least 35 years to ac- Kijas JMH, Thomas MR, Fowler JCS, and Roose ML, Gallil 1972; Jolls and Chenier 1989; Koelew- complish, compared to several hundred 1997. Integration of trinucleotide microsatellites into a ijn and Van Damme 1995a; Philipp 1980). linkage map of Citrus. Theor Appl Genet 94:701–706. years for C. alta. The last type is generally called ‘‘gyno- Primmer CR, Raudsepp T, Chowdhary BP, Moller AP, Random physical distributions of mark- and Ellegren H, 1997. Low frequency of microsatellites monoecious’’ or ‘‘partially male sterile.’’ er loci is an important assumption of pop- in the avian genome. Genome Res 7:471–482. The term ‘‘gynodioecy’’ was originally ulation genetic studies as well as a re- Sokal RR and Rohlf FJ, 1981. Biometry, 2nd ed. New coined to describe the plant reproductive quirement for high-resolution genetic York: W.H. Freeman. system with only females and hermaph- mapping. For population genetic studies, Received May 13, 1998 rodites (Darwin 1877). Formally speaking, marker loci should be drawn from as Accepted March 31, 1999 populations containing individuals of the much of the genome as possible so evo- Corresponding Editor: Norman F. Weeden third type should therefore be said to lutionary events (mutation dynamics, phy- have a gynodioecious-gynomonoecious logenetic history, selection, and linkage) breeding system, but normally the occur- Downloaded from https://academic.oup.com/jhered/article/90/5/563/2186975 by guest on 27 September 2021 are averaged across the genome. The use rence of such plants is disregarded and of multiple restriction enzymes or the re- Female and Hermaphrodite the breeding system is still said to be duction of sampling steps when construct- gynodioecious. The standard explanation ing the DNA insert pool may increase the Flowers on a Chimeric of gynomonoecious plants is that they rep- diversity of SSR marker loci available. Gynomonoecious Silene resent the developmental outcome of an These results suggest that SSR loci bear- vulgaris Plant Produce incomplete restoration by nuclear male ing different repeats are not associated fertility genes of male-sterilizing cyto- within the genome, so the use of SSR Offspring with Different plasms (Koelewijn and Van Damme 1995b; marker loci with different repeats may aid Genders: A Case of Louis and Durand 1978; Van Damme 1983; in meeting the assumption of randomness Heteroplasmic Sex Vranceanu and Stoenescu 1978; Wicker- for population genetic studies. Although Determination? sham and Patterson 1980). the genomic distribution of SSR loci is less Silene vulgaris (Moench) Garcke (Cary- of a concern in parentage analysis appli- H. Andersson ophyllaceae), a common weed in ruderate cations (as long as markers are unlinked), habitats throughout Europe, is usually re- using multiple restriction enzymes when In gynodioecious plant species, individu- ferred to as being gynodioecious, though constructing DNA libraries may increase als have either female or hermaphrodite gynomonoecious individuals have fre- the diversity of SSRs available. flowers. However, individuals with both quently been observed (Brockman and From the Smithsonian Institution, National Zoological types of flowers, that is, ‘‘gynomonoe- Bocquet 1978; Charlesworth and Laporte Park, Molecular Genetics Laboratory, Washington, DC. cious’’ or ‘‘partially male steriles,’’ are 1998; Dulberger and Horovitz 1984; Jolls This work was supported by a Smithsonian Institution sometimes found. The standard explana- and Chenier 1989). The full genetic details postdoctoral fellowship to M.B.H. and Friends of the National Zoo. We thank D. Fonseca and L. Shapiro for tion of gynomonoecious individuals is that of the sex determination system in the contributions to the microsatellite cloning methods, I. their male-sterilizing cytoplasm is incom- species is not yet fully understood. There Jones for help picking colonies, and J. Ballou for dis- pletely restored by nuclear male fertility is, however, strong evidence that both nu- cussion of G tests. W. J. Kress provided tissue samples of H. acuminata and helpful discussion. Two anony- genes. Silene vulgaris, the bladder cam- clear and cytoplasmic factors are involved mous reviewers provided comments that improved the pion, is usually referred to as being gyno- in the determination of sex (Charlesworth manuscript. Address correspondence to M. B. Hamil- ton, Georgetown University, Department of Biology, dioecious, though gynomonoecious indi- and Laporte 1998; Marsden-Jones and Tur- Reiss Building STE 406, Box 571229, Washington DC viduals have frequently been observed. In ill 1957). 20057-1229, or e-mail: [email protected]. an attempt to determine if the segregation In a survey of S. vulgaris plants in natu- ᭧ 1999 The American Genetic Association of flower types on gynomonoecious plants ral populations from southern Sweden, gy- of S. vulgaris is associated with a differ- nomonoecious individuals were found to- ence in offspring gender, a series of cross- gether with females and hermaphrodites. References es was performed. The results show that Seeds were collected from the populations Arens P, Odinot P, van Heusden AW, Lindhout P, and Vosman B, 1995. GATA- and GACA-repeats are not even- female and hermaphroditic flowers on the and plants were raised under standard ly distributed throughout the tomato genome. Genome same plant produce offspring of all three conditions in a greenhouse. At flowering 38:84–90. types, but the frequencies with which they the frequencies of gynomonoecious, fe- Armour JAL, Neumann R, Gobert S, and Jeffreys AJ, do so differ. If incomplete restoration was male, and hermaphroditic plants were de- 1994. Isolation of human simple repeat loci by hybrid- ization selection. Hum Mol Genet 3:599–605. the relevant explanation in this case, these termined. In the different populations gy- Bell CJ and Ecker, JR, 1994. Assignment of 30 microsa- results would not have occurred. Instead nomonoecious plants ranged in frequency tellite loci to the linkage map of Arabidopsis. Genomics an intraindividual segregation of one or from 0 to 25%, while female plant frequen- 19:137–144. many genetic factors that affect the sexual cy ranged from 0 to 90%. Three types of Fleischer RC and Loew S, 1995. Construction and phenotype of flowers and their subse- flower stalks could be observed on the gy- screening of microsatellite-enriched genomic libraries. In: Molecular zoology: advances, strategies and proto- quent offspring is proposed. nomonoecious individuals: stalks with cols (Ferraris J and Palumbi S, eds). New York: Wiley- only female flowers, stalks with only her- Liss; 461–468. Three different genders are frequently maphrodite flowers, and stalks with a mix- Goldstein DB and Pollock DD, 1997. Launching microsatellites: a review of the mutation processes and found in gynodioecious species: plants ture of both types of flowers. The ratio of methods of phylogenetic inference. J Hered 88:335–342. with only female flowers, plants with only female to hermaphrodite flowers on the Kijas JMH, Fowler JCS, Thomas MR, and Garbett CA, hermaphrodite flowers, and plants with gynomonoecious plants varied, as did the Brief Communications 563 Table 1. The gender of offspring to four sets of crosses between a chimeric gynomonoecious plant (A) and two hermaphrodite test plants (M and N)ofS. vulgaris Offspring gender Test of homogeneity Gynomo- Herma- Crosses Female noecious phrodite Total ␹2 p Figure 1. Typical flower arrangements in chimeric 1. A (self-fertilized) branches of gynomonoecious S. vulgaris plants. Filled a. Female flowers 50 6 8 64 13.0 Ͻ.01 circles represent hermaphroditic flowers; unfilled cir- b. Hermaphroditic flowers 44 28 8 80 cles represent female flowers. 2. A ϫ M a. Female flowers 64 2 30 96 30.6 Ͻ.001 degree of maleness of the individual her- b. Hermaphroditic flowers 32 22 46 100 maphroditic flowers (as judged by the 3. A ϫ N number and size of anthers). The segre- a. Female flowers 60 2 37 99 10.9 Ͻ.01 b. Hermaphroditic flowers 52 15 32 99 gation of female and hermaphroditic flow- 4. A (self-fertilized) ers on chimeric stalks often showed a Downloaded from https://academic.oup.com/jhered/article/90/5/563/2186975 by guest on 27 September 2021 a. Female flowers 49 20 6 75 — — strikingly symmetrical pattern (Figure 1). b. Hermaphroditic flowers — — — — Even though the ratio of female to hermaphroditic flowers on gynomonoecious In crosses 1, 2, and 3 the female flowers came from female stalks and the hermaphroditic flowers from hermaphrodite stalks. Castrations were made in crosses 2 and 3 to avoid self-fertilization. The homogeneity between off- plants varied from one period of flowering spring classes was investigated with a chi-square test with two degrees of freedom. In the fourth cross, the flowers to the next, their gender expression was used to set seeds came from chimeric stalks; no seeds were produced by the hermaphroditic flowers. The pollen used for self-fertilizing plant A (crosses 1 and 4) came from hermaphroditic flowers on hermaphroditic flower stable over years. stalks. To determine if the segregation of flowers on gynomonoecious plants of S. vulgaris is associated with a difference in the analogous to the second cross but in hermaphroditic flowers produce more gy- offspring types produced, a series of which plant N was used as the pollen do- nomonoecious offspring than female flow- crosses was performed. A typical gyno- nor, the same differences in offspring gen- ers do. When the flowers from chimeric monoecious individual (A) and two her- der were seen. In general, the proportion stalks are studied, it is seen that female maphroditic test plants (M and N) were of hermaphrodites among the offspring in- flowers from such stalks produce more gy- used as parents in the crosses.

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