Browsing by Author "Zeru Zelelew, Daniel"

The sunflower family (Asteraceae) is characterized by its unique head-like inflorescence known as a capitulum. The capitula have evolved enormous diversity in size and shapes, and such variability depends upon the inflorescence meristem (IM) patterning. Gerbera hybrida has emerged as one of the model species for the large Asteraceae plant family. Previous studies have reported that the inflorescence architecture of gerbera has both conserved and derived gene regulatory features. So far, several studies have revealed that some genes, which have highly specialized functions in regulating Arabidopsis flower development, are represented by expanded gene families in gerbera and gained new functions at the level of IM. IM determinacy refers to the fate of the meristem to continue growing indefinitely or to terminate into a flower. However, there is still a significant knowledge gap to understand regulation of IM determinacy in Asteraceae. This research aims to explore the expression of the gerbera GSQUA genes and their potential interactions with the key regulators, GhLFY, GRCD2, GRCD7, and GhTFL1, in the patterning of IM of wild-type (WT) gerbera. The study also involved the phenotypic characterization of GhTFL1 overexpression and GhTFL1 RNAi transgenic lines. The results showed that GSQUA2, GSQUA3, and GSQUA7 had similar expression patterns with GhLFY and were expressed throughout the IM and involucral bract, ray, and disc floret primordia. The expression of GSQUA5, which resembles the expression of GRCD2 and GRCD7, started from IM2 and was upregulated throughout the inflorescence development. GRCD6 and GRCD8 exhibited an early and much broader range of expression patterns than the other GSQUAs. Meanwhile, GhTFL1 was expressed only in the shoot apical meristem and IM1. Results from the phenotypic analysis of the GhTFL1 transgenic lines showed that both ectopic and suppressed GhTFL1 expression lines have altered inflorescence architecture. Overexpression of GhTFL1 resulted in the formation of a dome-shaped indeterminate IM, which is not consumed by floral primordia. Severe GhTFL1 RNAi phenotypes show a very small determinate inflorescence that is entirely consumed, with a terminal flower developed at the center. The expression patterns and interaction of GSQUA genes with GhLFY, GRCD2, GRCD7, and GhTFL1 indicated that GSQUA2/3/5/7 are the most promising candidates for regulating IM patterning and determinacy of gerbera. Besides, the findings underscore the crucial role of GhTFL1 in regulating the inflorescence architecture of gerbera and significantly advance our understanding of genetic regulation of IM determinacy in the Asteraceae family.