752 / 2019-05-16 03:10:44

Nitrate control of organ size in Arabidopsis thaliana

cell cycle,nutrition,growth,leaves

全体主题 > Nutrition

Precise coordination of cell expansion and cell proliferation underlies growth in multicellular organisms. In addition to endogenous developmental programs, external environmental signals are integrated to modulate organ growth in plants. Nitrate is a nitrogen nutrient that can act as a potent signal to modulate shoot growth, yet the mechanisms are largely unexplored in Arabidopsis thaliana and other plant species. Herein we show that nitrate regulates cotyledon and leaf growth by modulating cell size and endoreplication. We identified a key cell cycle regulatory (CCR) factor influencing ploidy and cell-size depending on external nitrate. Nitrate induces CCR gene expression as early as 3 days after germination in epidermal and mesophyll cell layers which undergo endoreplication to increment cell size and DNA content. Surprisingly, while endoreplicaiton and cell size are greatly reduced in ccr mutant plants, cotyledon size defined by external nitrate supply is independent of CCR. In ccr mutant plants where cells are unable to endoreplicate, cotyledon organ size is achieved through cell division. Our results indicate that nitrate generally controls cotyledon and leaf size by increasing ploidy levels and cell expansion, but that cell division can be substituted for endoreplication without affecting organ size or growth. Moreover, our results indicate nitrate interacts with an organ-level growth control mechanism to define organ size in Arabidopsis thaliana.