Isolation and characterization of GIGANTEA homolog in Pharbitis nil, a short day plant

Abstract

GIGANTEA (GI) is one of the key regulators of flowering time, which is closely related to the circadian clock function in Arabidopsis. In this study, we cloned P. nil homolog of GI (PnGI), which encoded a putative polypeptide of 1166 amino acids. The deduced amino acid sequence of PnGI showed 70% and 67% amino acid identity with those of Arabidopsis and rice, respectively. PnGI expression showed robust circadian rhythms under both continuous dark (DD), and continuous light (LL) conditions. Under short-day (SD) and long-day (LD) conditions, PnGI expression was increased during the light phase, peaking at dusk. These expression patterns of PnGI are very similar to those of GI and OsGI, suggesting that conserved mechanisms for the regulation of GI mRNA expression may exist in various plant species.