• 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.

中文翻译：

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生长素外排控制拟南芥雌性配子体有序的细胞核退化和扩张

• 开花植物中的珠心组织为雌配子体 (FG) 和幼胚的发育提供营养。珠心随着 FG 的发展而退化，但控制珠心退化和 FG 扩张耦合过程的机制在很大程度上仍是未知的。
• 研究了拟南芥受精前胚珠的退化过程和发育中胚珠中生长素的时空分布。
• 受精前的细胞核变性通过液泡细胞死亡并以有序的变性方式发生。这种连续的细胞核退化由信号分子生长素控制。
• 生长素外排在精确控制 FG 周围细胞核中生长素分布的时空模式方面起着核心作用。生长素外排载体 PIN1 将母体生长素转运到细胞核中，而 PIN3/PIN4/PIN7 进一步将生长素输送到退化的细胞核中，同时控制 FG 中央液泡扩张。值得注意的是，生长素浓度和生长素流出受母体组织控制，充当从母体到子体组织的关键通信。