A paper entitled GRF-interacting Factor1 (gif1) Regulates Shoot Architecture and Meristem Determinacy in Maize, which revealed the molecular mechanism of gif1’s regulating the number of inflorescence branches in maize by combining with the key gene unbranched3 (ub3), was published on The Plant Cell, on February 05, 2018. The work was cooperatively achieved by Prof. Zuxin Zhang of the maize group of National Key Laboratory of Crop Genetic Improvement in HZAU and Prof. Sarah Hake of California-Berkeley University. PhD students of HZAU Dan Zhang and Dr. Wei Sun are the co-first author.
Plant architecture results from a balance of indeterminate and determinate cell fates. Cells with indeterminate fates are located in meristems, comprising groups of pluripotent cells that produce lateral organs. The shoot apical meristem is an indeterminate meristem, initiating primordia indefinitely. Floral meristems are considered determinate, as they terminate after the production of floral organs. Most developmental mutants identified so far affect one or two parts of the phytomer and rarely play a role in multiple aspects of shoot architecture. In the paper, researchers identified a pleiotropic maize (Zea mays) mutant that affects multiple meristems in different ways. The gif1 mutation affects both lateral organs and meristems: mutants have narrow leaves, short internodes, fewer tassel branches, and indeterminate axillary meristems compared to wild type. Importantly, the phenotypes of the male and female inflorescences were significantly different, with long branches of female inflorescences increasing, while the male inflorescence branches were reduced and inflorescence meristems were enlarged.Studies show that, gif1 was expressed in actively dividing cells at the apical and inflorescence meristems and overlaps with the expression patterns of ramosa2 (ra2) and unbranched3 (ub3). ChIP-seq analysis of male inflorescence revealed that GIF1 binds directly to the ub3 promoter and regulates the size and number of branches of male inflorescences by regulating ub3 expression. The mechanism that GIF1 differentially regulates male and female inflorescence branches remains to be further revealed.
