Inflorescence morphogenesis

Abstract: Organ development in plants predominantly occurs postembryonically through combinatorial activity of meristems; therefore, meristem and organ fate are intimately connected. Inflorescence morphogenesis in grasses (Poaceae) is complex and relies on a specialized floral meristem, called spikelet meristem, that gives rise to all other floral organs and ultimately the grain. The fate of the spikelet determines reproductive success and contributes toward yield-related traits in cereal crops. Here, we examined the transcriptional landscapes of floral meristems in the temperate crop barley (Hordeum vulgare L.) using RNA-seq of laser capture microdissected tissues from immature, developing floral structures. Our unbiased, high-resolution approach revealed fundamental regulatory networks, previously unknown pathways, and key regulators of barley floral fate and will equally be indispensable for comparative transcriptional studies of grass meristems.

Abstract: MADS-box genes play an important role in plant ontogeny, particularly, in the regulation of floral organ induction and development. Eight full-length cDNAs of HAM genes (HelianthusannuusMADS) have been isolated from sunflower. They encode MADS-box transcription factors expressed in inflorescence tissues. In the frames of the ABCDE model, the HAM proteins were classified according to their structural homology to known MADS-box transcription factors. The HAM45 and HAM59 genes encode the homeotic C function and are involved in the control of the identity of pistil and stamens, while the HAM75 and HAM92 genes determine the A function and identity of floral and inflorescence meristems and petal identity. The HAM31, HAM2, HAM63, and HAM91 genes encode the B function and are involved in the formation of petals and stamens; and the HAM137 gene encodes the E function. Analysis of the expression of HAM genes in sunflower has demonstrated that the structural and functional differences between the ray and tubular flowers in the inflorescence could be a consequence of the lack of HAM59 expression during ray flower initiation

Abstract: Architectural development of inflorescence in Hydrangea macrophylla cv. Hermann Dienemann was observed using scanning electron microscopy. The study of inflorescence morphogenesis shows that the architecture is of the dichasial type. The first two orders of branching are initiated from a dichasial branching without floral differentiation. The following orders present floral differentiation. They determine the formation of small units through the development of composite dichasium into biparous and uniparous cymes. This research makes it possible to establish a schematic representation of the first phases of inflorescence development and to define early stages of inflorescence morphogenesis.

Abstract: Maize (Zea mays) is a monoecious plant, in which inflorescence morphogenesis involves complicated molecular regulatory mechanisms. Although many related genes have been cloned, our understanding of the molecular mechanism underlying maize inflorescence development remains limited. Here, we identified a maize semi-dominant mutant Silky3 (Si3), which displays pleiotropic defects during inflorescence development, including loss of determinacy and identity in meristems and floral organs, as well as the sexual transformation of tassel florets. We cloned the si3 gene using a map-based approach. Functional analysis reveals that SI3 is a nuclear protein and may act as a transcriptional regulator. Transcriptome analysis reveals that the ectopic expression of si3 strongly represses multiple biological processes, especially the flower development pathways. RNA in situ hybridization similarly shows that the expression patterns of genes responsible for flower development are changed in the Si3 mutant. In addition, the homeostasis of jasmonic acid and gibberellic acid are altered in the Si3 young tassels, and application of exogenous jasmonic acid can rescue the sex reversal phenotype of Si3 The defects we characterized in various regulatory pathways can explain the complex phenotypes of Si3 mutant, and this study deepens our knowledge of maize inflorescence development.