Dissecting functions of SEPALLATA‐like MADS box genes in patterning of the pseudanthial inflorescence of Gerbera hybrida

Abstract

The pseudanthial inflorescences of the sunflower family, Asteraceae, mimic a solitary flower but are composed of multiple flowers. Our studies in Gerbera hybrida indicate functional diversification for SEPALLATA (SEP)-like MADS box genes that often function redundantly in other core eudicots. We conducted phylogenetic and expression analysis for eight SEP-like GERBERA REGULATOR OF CAPITULUM DEVELOPMENT (GRCD) genes, including previously unstudied gene family members. Transgenic gerbera plants were used to infer gene functions. Adding to the previously identified stamen and carpel functions for GRCD1 and GRCD2, two partially redundant genes, GRCD4 and GRCD5, were found to be indispensable for petal development. Stepwise conversion of floral organs into leaves in the most severe RNA interference lines suggest redundant and additive GRCD activities in organ identity regulation. We show conserved and redundant functions for several GRCD genes in regulation of flower meristem maintenance, while functional diversification for three SEP1/2/4 clade genes in regulation of inflorescence meristem patterning was observed. GRCD genes show both specialized and pleiotropic functions contributing to organ differentiation and flower meristem fate, and uniquely, to patterning of the inflorescence meristem. Altogether, we provide an example of how plant reproductive evolution has used conserved genetic modules for regulating the elaborate inflorescence architecture in Asteraceae.

Genome‐wide analysis of MADS‐box family genes during flower development in lettuce

“…The encoded protein can interact with B‐ and E‐class proteins to influence stamen and carpel development, respectively. Eight SEP ‐like genes are functionally redundant regarding their effects on inflorescence patterns in G. hybrida (Zhang, Zhao, et al, ). Five lettuce SEP genes were widely expressed in the flower primordia, and the encoded proteins interacted with ABCE class proteins.…”

“…Bracts protecting the inflorescence exhibit sepal characteristics, but they are not associated with any flower whorl. (Zhang et al, ).…”

High-resolution temporal transcript profiling duringArabidopsis thalianagynoecium morphogenesis uncovers the chronology of gene regulatory network activity and reveals novel developmental regulators

“…Severe subfunctionalization and extreme reduction in expression of SEP genes was also observed in several plant species, for example in Gerbera hybrida, whose genome includes seven SEP genes. While one of them, GRCD6, is hardly expressed, the other six genes diverge strongly in their expression pattern and function, and several distinct phenotypes were observed in the gynoecium when individual SEP genes were downregulated (Zhang et al, 2017). Gene duplication followed by subfunctionalization thus seems to be common to SEP homologs.…”

An ETHYLENE INSENSITIVE3-LIKE1 Protein Directly Targets the GEG Promoter and Mediates Ethylene-Induced Ray Petal Elongation in Gerbera hybrida

“…It has an inflorescence typically consisting of three different types of florets, which from outside to the inside are ray florets, trans florets, and disc florets. This head-like inflorescence structure is very different from that of the classical model plant Arabidopsis, and G. hybrida is regarded as a new model for floral organ developmental studies, particularly among the Asteraceae (Shepard and Purugganan, 2002;Buzgo et al, 2004;Zhang et al, 2017).…”