Exploring flowering and photoperiod response mechanisms in legumes

Contreras B, Van der Schoor J, Hecht V and Weller JL

School of Natural Sciences, University of Tasmania, Hobart, Tasmania, Australia.

Flowering time and its responsiveness to photoperiod is a key trait in the adaptation of plants to different climates and locations. The genetic control of flowering is well described in the model plant Arabidopsis but not as well understood in other species including many crops. Legumes are an important crop group that includes two clades showing opposite response to photoperiod: warm season species such as soybean and bean, which are short-day plants, and temperate species such as chickpea and pea which are long-day plants. Pea (Pisum sativum) has been an important model system for investigating the legume long-day mechanism and exploring similarities and differences with the main Arabidopsis model. Previous studies have characterized an expanded family of FT (florigen) genes pea that collectively play a conserved role as environmentally-regulated mobile flowering signals. Certain upstream regulators of FT genes are also conserved with Arabidopsis, but a key difference is the lack of a clear role for homologs of CONSTANS (CO), which in Arabidopsis is a major FT activator that integrates light and circadian clock signalling for photoperiod measurement. The absence of this central point of regulation raises questions about the nature of the molecular mechanism for photoperiod response in pea and how other conserved components may be acting. This study investigates two specific aspects of this system in order to further assess the conservation of photoperiod-response pathways; 1) the role of the pea ortholog of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a major regulator of CO protein stability in Arabidopsis and 2) the mechanism of action of LATE BLOOMER 1 (LATE1), an ortholog of Arabidopsis GIGANTEA which has an important role in regulating CO transcription.