第1224回生物科学セミナー
An interconnection of cell proliferation-mediated leaf size and inhibition of senescence progression during leaf growth
Prof. Gyung-Tae Kim（Dong-A University, Korea）
2018年07月18日(水) 16:50-18:35 理学部2号館 講堂
Leaf growth and size are determined through the coordination process of cell proliferation and cell expansion, but its molecular details are still fragmentary. Our study of Kip-related protein (KRP), which is a negative regulator of cell cycle, indicated that inhibition of cell proliferation affected cell expansion in leaves through two independent processes; 1) endoreduplication by increasing DNA ploidy level, 2) compensation syndrome without change of DNA ploidy. In contrast, our recent study of Arabidopsis thaliana homeobox 12 transcription factor positively controlled endoreduplication and cell expansion without change of cell proliferation, thereby promoting leaf organ growth.
After subsequent growth and maturation, on the other hand, leaves undergo a programmed event to senescence, but our knowledge of the interrelationship between leaf growth and senescence is still unknown. Here, we showed the oresara15-1Dominant (ore15-1D) mutant, which was isolated from Arabidopsis activation-tagged lines, had a delayed leaf senescence and enlarged leaves. From our molecular genetic- and anatomical- analyses, we identified that ORE15 encoded a novel PLATZ transcription factor and enhanced leaf growth by promoting cell proliferation in the earlier stage and suppressed leaf senescence in the later stage by modulating GROWTH-REGULATING FACTOR (GRF)/GRF-INTERACTING FACTOR (GIF) regulatory pathway. Our study highlighted a molecular conjunction through ORE15 between two temporally separated developmental processes during leaf lifespan, growth and senescence. Together, we will discuss a coordination between cell proliferation and cell expansion; and an interconnection of cell proliferation-mediated leaf size and inhibition of senescence progression.
