The developmental programs of Physcomitrella patens, a basal lineage of land plants, are regulated by phytohormones and light-signaling responses. In this study, our attention was focused on the HY5-family of transcription factors, which are known to play important roles immediately downstream of photoreceptors during the early photomorphogenesis of Arabidopsis thaliana. We retrieved two HY5-homologs, named PpHY5a and PpHY5b, from the whole genome sequence database of P. patens. Arabidopsis transgenic plants overproducing the basic leucine zipper (bZIP) domain of PpHY5a exhibited a phenotype of short hypocotyls, suggesting a functional relationship between PpHY5 and Arabidopsis HY5. A loss-of-function Áhy5a Áhy5b double mutant was defective in the vigorous protrusion of caulonema cells from the protonema networks of P. patens under light and dark conditions. These results suggest that the function of HY5-homologs in P. patens is evolutionarily conserved, and is implicated in a process of caulonema development.
During the last decade, significant research progress in the study of Arabidopsis thaliana has been made in defining the molecular mechanism by which the plant circadian clock regulates flowering time in response to changes in photoperiod. It is generally accepted that the clock-controlled CONSTANS (CO)-FLOWERING LOCUS T (FT)-mediated external coincidence mechanism underlying the photoperiodic control of flowering time is conserved in higher plants, including A. thaliana and Oryza sativa. However, it is also assumed that the mechanism differs considerably in detail among species. Here we characterized the clock-controlled CO-FT pathway in Lotus japonicus (a model legume) in comparison with that of A. thaliana. L. japonicus has at least one FT orthologous gene (named LjFTa), which is induced specifically in long-days and complements the mutational lesion of the A. thaliana FT gene. However, it was speculated that this legume might lack the upstream positive regulator CO. By employing L. japonicus phyB mutant plants, we showed that the photoreceptor mutant displays a phenotype of early flowering due to enhanced expression of LjFTa, suggesting that LjFTa is invovled in the promotion of flowering in L. japonicus. These results are discussed in the context of current knowledge of the flowering in crop legumes such as soybean and garden pea.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.