月季花瓣数量遗传分析

以‘窄叶藤本月季花’( Rosa chinensis ‘Zhaiye Tengben Yuejihua’)ב月月粉’( R. chinensis ‘Old Blush’)杂交群体为材料, 分析其花瓣数量的分离特点, 对单瓣花与重瓣花的花芽分化过程进行观察, 并对花瓣、雄蕊及瓣化雄蕊进行表皮细胞超微结构的观察.结果显示...     

Functional and evolutionary analyses of Primulina heterotricha CYC1C gene in tobacco and Arabidopsis transformation systems

In Asterids, specific expression of CYC-like genes in the corresponding regions promotes or reduces dorsal petal growth and aborts stamen development. In Rosids, however, the reduced or enlarged dorsal petals are not accompanied by the abortion of stamens, which implies that the function of CYC-like genes in regulating petal growth and stamen development might be independently recruited. To address this, we investigated the function of the PhCYC1C gene in Primulina heterotricha Y. Dong & Y. Z. Wang on petal growth and stamen development by overexpressing it in two different transformation systems, that is, Arabidopsisbelonging to Rosids and tobacco located in Asterids. The results showed that overexpression of PhCYC1C reduced petal sizes in both tobacco and Arabidopsistransgenic plants mainly by repressing cell expansion, indicating its conserved function in determining petal growth between Asterids and Rosids. However, the fertility of both tobacco and Arabidopsis stamens was not affected at all. Given that strong expression signals of PhCYC1C are detected in both tobacco andArabidopsis stamens and CYC-like genes actually function to repress stamen development in Lamiales, we suggest that the CYC-like gene-associated regulatory network for controlling stamen development might have not established in Rosids as well as in early evolution of Asterids, but evolved as Asterids proceeded further. Our results provide valuable information on the conservation of CYC-like genes' function in controlling corolla asymmetry and the divergence of their function in determining stamen abortion in angiosperms.     

NORMAL FLORAL ONTOGENY AND COOL TEMPERATURE-INDUCED ABERRANT FLORAL DEVELOPMENT IN GLYCINE MAX (FABACEAE)

Floral onset in soybean (Glycine max cv. Ransom) is characterized by precocious initiation of axillary meristems in the axils of the most recently initiated leaf primordium. During floral transition, leaf morphology changes from trifoliolate leaf with stipules, to a three-lobed bract, to an unlobed bract. Soybean flowers initiated at 26/22 C day/night temperatures are normal, papilionaceous, and pentamerous. Sepal, petal, and stamen whorls are initiated unidirectionally from the abaxial to adaxial side of the floral apex. The median sepal is located abaxially and the median petal adaxially on the meristem. The organogeny of ‘Ransom’ flowers was found to be: sepals, petals, outer stamens plus carpel, inner stamens; or, sepals, petals, carpel, outer stamens, inner stamens. The outer stamen whorl and the carpel show possible overlap in time of initiation. Equalization of organ size occurs only within the stamen whorls. The sepals retain distinction in size, and the petals exhibit an inverse size to age relationship. The keel petals postgenitally fuse along part of their abaxial margins; their bases, however, remain free. Soybean flowers initiated at cool day/night temperatures of 18/14 C exhibited abnormalities and intermediate organs in all whorls. The gynoecium consisted of one to ten carpels (usually three or four), and carpel connation varied. Fusion of keel petals was often lacking, and stamen filaments fused erratically. Multiple carpellate flowers developed into multiple pods that were separate or variously connate. Intermediate type organs had characteristics only of organs in adjacent whorls. These aberrant flowers demonstrate that the floral meristem of soybean is not fixed or limited in its developmental capabilities and that it has the potential to produce alternate morphological patterns.     

Comparative floral ontogeny in Detarieae (Leguminosae: Caesalpinioideae). 2. Zygomorphic taxa with petal and stamen suppression

Marked floral zygomorphy and a reduced number of petals and/or stamens are the character traits that distinguish the taxa described (species of Afzelia, Berlinia, Gilbertiodendron, Macrolobium, Neochevalierodendron, Paramacrolobium, Phyllocarpus, and Tetraberlinia). All have an "Omega"-shaped floral apex after bracteole initiation, bracteoles large when initiated, helical sepal initiation, unidirectional petal initiation (simultaneous in Afzelia, not determinable in Tetraberlinia), and unidirectional stamen initiation. Floral zygomorphy is expressed primarily by one petal being much larger than the others and by suppression of several of the stamens. Five petals are initiated in all; suppression begins in late development. Either two petals (Neochevalierodendron, Phyllocarpus) or four petals (Afzelia, Berlinia, Macrolobium, Tetraberlinia) are suppressed. All ten stamens are initiated; at midstage, suppression begins in either three stamens (Afzelia) or seven stamens (Gilbertiodendron, Macrolobium, Paramacrolobium). Other expressions of zygomorphy may include diadelphy, stamen filament connation late in development, or displacement of the carpel from a central position to the adaxial side of the hypanthium. There is no loss of organs similar to that which occurs in some other Detarieae.     

单瓣与重瓣垂丝海棠花器官形态发育比较观察

为探究垂丝海棠重瓣花成花原因,该研究以单瓣垂丝海棠和重瓣垂丝海棠为实验材料,应用体式显微镜和扫描电镜观察垂丝海棠单瓣、重瓣品种花器官分化过程;解剖观察重瓣垂丝海棠大蕾期的花与盛开的花,统计其花器官的形态与数目;应用R语言对重瓣垂丝海棠的花瓣数目与其余各轮花器官数目进行相关性分析。结果显示：(1)单瓣和重瓣垂丝海棠的花器官分化均分为萼片原基分化期、花瓣原基分化期、雄蕊原基分化期、雌蕊原基分化期,且各轮花器官按照向心顺序依次分化发育。(2)在花瓣原基分化期,单瓣垂丝海棠仅分化出一轮(5枚)均匀分布于两枚萼片交汇处的花瓣原基,而重瓣垂丝海棠分化出两轮分布散列的花瓣原基,第一轮为5~7枚,第二轮为7~10枚。(3)在重瓣垂丝海棠各轮花器官中存在较多萼片瓣化、雄蕊瓣化、雌雄蕊异常发育的情况。(4)重瓣垂丝海棠各轮花器官数目间相关性分析结果显示,其花瓣数目与雄蕊数目以及瓣化中的雄蕊数目间存在明显的正相关关系,该现象与常规雄蕊瓣化植物表现的雄蕊数目减少、花瓣数目增多的现象不同。研究表明,重瓣垂丝海棠花瓣数目的增多并不完全依赖于雄蕊变瓣,暗示垂丝海棠重瓣花成花原因的多元性与复杂性。     

To B or Not to B a flower: the role of DEFICIENS and GLOBOSA orthologs in the evolution of the angiosperms

DEFICIENS (DEF) and GLOBOSA (GLO) function in petal and stamen organ identity in Antirrhinum and are orthologs of APETALA3 and PISTILLATA in Arabidopsis. These genes are known as B-function genes for their role in the ABC genetic model of floral organ identity. Phylogenetic analyses show that DEF and GLO are closely related paralogs, having originated from a gene duplication event after the separation of the lineages leading to the extant gymnosperms and the extant angiosperms. Several additional gene duplications followed, providing multiple potential opportunities for functional divergence. In most angiosperms studied to date, genes in the DEF/GLO MADS-box subfamily are expressed in the petals and stamens during flower development. However, in some angiosperms, the expression of DEF and GLO orthologs are occasionally observed in the first and fourth whorls of flowers or in nonfloral organs, where their function is unknown. In this article we review what is known about function, phylogeny, and expression in the DEF/GLO subfamily to examine their evolution in the angiosperms. Our analyses demonstrate that although the primary role of the DEF/GLO subfamily appears to be in specifying the stamens and inner perianth, several examples of potential sub- and neofunctionalization are observed.     

Functional specialization of duplicated AP3‐like genes in Medicago truncatula

The B–class of MADS box genes has been studied in a wide range of plant species, but has remained largely uncharacterized in legumes. Here we investigate the evolutionary fate of the duplicated AP3‐like genes of a legume species. To obtain insight into the extent to which B‐class MADS box gene functions are conserved or have diversified in legumes, we isolated and characterized the two members of the AP3 lineage in Medicago truncatula: MtNMH7 and MtTM6 (euAP3 and paleoAP3 genes, respectively). A non‐overlapping and complementary expression pattern of both genes was observed in petals and stamens. MtTM6 was expressed predominantly in the outer cell layers of both floral organs, and MtNMH7 in the inner cell layers of petals and stamens. Functional analyses by reverse genetics approaches (RNAi and Tnt1 mutagenesis) showed that the contribution of MtNMH7 to petal identity is more important than that of MtTM6, whereas MtTM6 plays a more important role in stamen identity than its paralog MtNMH7. Our results suggest that the M. truncatula AP3‐like genes have undergone a functional specialization process associated with complete partitioning of gene expression patterns of the ancestral gene lineage. We provide information regarding the similarities and differences in petal and stamen development among core eudicots.     

Floral development of petaloid Alismatales as an insight into the origin of the trimerous Bauplan in monocot flowers

Monocots are remarkably homogeneous in sharing a common trimerous pentacyclic floral Bauplan. A major factor affecting monocot evolution is the unique origin of the clade from basal angiosperms. The origin of the floral Bauplan of monocots remains controversial, as no immediate sister groups with similar structure can be identified among basal angiosperms, and there are several possibilities for an ancestral floral structure, including more complex flowers with higher stamen and carpel numbers, or strongly reduced flowers. Additionally, a stable Bauplan is only established beyond the divergence of Alismatales. Here, we observed the floral development of five members of the three ‘petaloid’ Alismatales families Butomaceae, Hydrocharitaceae, and Alismataceae. Outer stamen pairs can be recognized in mature flowers of Alismataceae and Butomaceae. Paired stamens always arise independently, and are either shifted opposite the sepals or close to the petals. The position of stamen pairs is related to the early development of the petals. In Butomaceae, the perianth is not differentiated and the development of the inner tepals is not delayed; the larger inner tepals (petals) only permit the initiation of stamens in antesepalous pairs. Alismataceae has delayed petals and the stamens are shifted close to the petals, leading to an association of stamen pairs with petals in so-called stamen–petal complexes. In the studied Hydrocharitaceae species, which have the monocot floral Bauplan, paired stamens are replaced by larger single stamens and the petals are not delayed. These results indicate that the origin of the floral Bauplan, at least in petaloid Alismatales, is closely linked to the position of stamen pairs and the rate of petal development. Although the petaloid Alismatales are not immediately at the base of monocot divergence, the floral evolution inferred from the results should be a key to elucidate the origin of the floral Bauplan of monocots.     

Molecular evolution of the petal and stamen identity genes, APETALA3 and PISTILLATA, after petal loss in the Piperales

Organ loss is an evolutionary phenomenon commonly observed in all kinds of multicellular organisms. Across the angiosperms, petals have been lost several times over the course of their diversification. We examined the evolution of petal and stamen identity genes in the Piperales, a basal lineage of angiosperms that includes the perianthless (with no petals or sepals) families Piperaceae and Saururaceae as well as the Aristolochiaceae, which exhibit a well-developed perianth. Here, we provide evidence for relaxation of selection on the putative petal and stamen identity genes, homologs of APETALA3 and PISTILLATA, following the loss of petals in the Piperales. Our results are particularly interesting as the B-class genes are not only responsible for the production of petals but are also central to stamen identity, the male reproductive organs that show no modification in these plants. Relaxed purifying selection after the loss of only one of these organs suggests that there has been dissociation of the functional roles of these genes in the Piperales.     

Negative regulation of the Arabidopsis homeotic gene AGAMOUS by the APETALA2 product.

We characterized the distribution of AGAMOUS (AG) RNA during early flower development in Arabidopsis. Mutations in this homeotic gene cause the transformation of stamens to petals in floral whorl 3 and of carpels to another ag flower in floral whorl 4. We found that AG RNA is present in the stamen and carpel primordia but is undetectable in sepal and petal primordia throughout early wild-type flower development, consistent with the mutant phenotype. We also analyzed the distribution of AG RNA in apetela2 (ap2) mutant flowers. AP2 is a floral homeotic gene that is necessary for the normal development of sepals and petals in floral whorls 1 and 2. In ap2 mutant flowers, AG RNA is present in the organ primordia of all floral whorls. These observations show that the expression patterns of the Arabidopsis floral homeotic genes are in part established by regulatory interactions between these genes.