Characterization of a gene from Zea mays related to the Arabidopsis flowering-time gene LUMINIDEPENDENS

The molecular biology of flowering has been most extensively studied in the quantitative long-day plant Arabidopsis thaliana. The Arabidopsis LUMINIDE PENDENS (LD) gene encodes a potential transcriptional regulator that acts a s a positive effector of flowering, at least in part through suppression of the floral inhibitor gene FLC. As an initial step to explore the conservat ion of the molecular mechanisms of flowering among plants of various flower ing habits, and to further investigate the molecular action(s) of LD, we ha ve identified a gene from maize (Zea mays) that is closely related to Arabi dopsis LD. The major product of this gene, which we have designated ZmLD fo r Zea mays LUMINIDEPENDENS, contains four conserved regions that may consti tute functionally important components of the LD proteins. One of these reg ions closely resembles the canonical homeodomain. The ZmLD gene exists as a single copy in the maize genome, and generates a major ca. 4.0 kb transcri pt, and a minor ca. 2.6 kb transcript that results from alternative transcr iptional termination. The 4.0 kb ZmLD alpha transcript accumulated to highe st levels in proliferative tissues, including the shoot apex and developing inflorescences. Expression of ZmLD alpha under control of the Arabidopsis LD promoter in transgenic Arabidopsis caused developmental defects similar to those conferred by loss-of-function mutations in a class of genes involv ed in maintaining the proliferative nature of the shoot, inflorescence, and floral meristems. These effects were not influenced markedly by the activi ties of the Arabidopsis LD or FLC genes. We consider the implications for t he conservation of LD function between maize and Arabidopsis.