State Key Laboratory of Crop Stress Biology for Arid Areas, College of Agronomy, Northwest A&F University, Yangling, Shaanxi, 712100, China.
Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA, 01003, USA.
New Phytol. 2021 Jun;230(6):2261-2274. doi: 10.1111/nph.17152. Epub 2021 Jan 18.
The nucellus tissue in flowering plants provides nutrition for the development of the female gametophyte (FG) and young embryo. The nucellus degenerates as the FG develops, but the mechanism controlling the coupled process of nucellar degeneration and FG expansion remains largely unknown. The degeneration process of the nucellus and spatiotemporal auxin distribution in the developing ovule before fertilization were investigated in Arabidopsis thaliana. Nucellar degeneration before fertilization occurs through vacuolar cell death and in an ordered degeneration fashion. This sequential nucellar degeneration is controlled by the signalling molecule auxin. Auxin efflux plays the core role in precisely controlling the spatiotemporal pattern of auxin distribution in the nucellus surrounding the FG. The auxin efflux carrier PIN1 transports maternal auxin into the nucellus while PIN3/PIN4/PIN7 further delivers auxin to degenerating nucellar cells and concurrently controls FG central vacuole expansion. Notably, auxin concentration and auxin efflux are controlled by the maternal tissues, acting as a key communication from maternal to filial tissue.
在开花植物中，珠心组织为雌配子体 (FG) 和幼胚的发育提供营养。随着 FG 的发育，珠心逐渐退化，但控制珠心退化和 FG 扩张的偶联过程的机制在很大程度上仍不清楚。本研究以拟南芥为材料，研究了受精前胚珠中珠心的退化过程和时空生长素分布。受精前的珠心退化是通过液泡细胞死亡和有序退化的方式发生的。这种顺序性的珠心退化受信号分子生长素的控制。生长素外排在精确控制 FG 周围珠心生长素的时空分布中起着核心作用。生长素外排载体 PIN1 将母体生长素运入珠心，而 PIN3/PIN4/PIN7 则将生长素进一步输送到退化的珠心细胞，并同时控制 FG 中央液泡的扩张。值得注意的是，生长素浓度和生长素外排受母体组织控制，是母体到子体组织的关键通讯。
