Autophagy is required for gamete differentiation in the moss <i>Physcomitrella patens</i>

Autophagy, a major catabolic process in eukaryotes, was initially related to cell tolerance to nutrient depletion. In plants autophagy has also been widely related to tolerance to biotic and abiotic stresses (through the induction or repression of programmed cell death, PCD) as well as to promotion of developmentally regulated PCD, starch degradation or caloric restriction important for life span. Much less is known regarding its role in plant cell differentiation. Here we show that macroautophagy, the autophagy pathway driven by engulfment of cytoplasmic components by autophagosomes and its subsequent degradation in vacuoles, is highly active during germ cell differentiation in the early diverging land plant <i>Physcomitrella patens.</i> Our data provide evidence that suppression of ATG5-mediated autophagy results in reduced density of the egg cell-mediated mucilage that surrounds the mature egg, pointing toward a potential role of autophagy in extracellular mucilage formation. In addition, we found that ATG5- and ATG7-mediated autophagy is essential for the differentiation and cytoplasmic reduction of the flagellated motile sperm and hence for sperm fertility. The similarities between the need of macroautophagy for sperm differentiation in moss and mouse are striking, strongly pointing toward an ancestral function of autophagy not only as a protector against nutrient stress, but also in gamete differentiation.

自噬（Autophagy）是真核生物的核心分解代谢途径，最初被发现与细胞耐受营养匮乏的能力相关。在植物中，自噬广泛参与生物胁迫与非生物胁迫的耐受过程（通过诱导或抑制程序性细胞死亡（programmed cell death, PCD）），同时还参与调控发育依赖的程序性细胞死亡、淀粉降解以及对寿命至关重要的热量限制等生理过程。目前学界对其在植物细胞分化中的作用仍知之甚少。本研究证实，巨自噬（macroautophagy）——即通过自噬体包裹细胞质组分并将其转运至液泡内降解的自噬通路——在早期分化陆生植物小立碗藓（Physcomitrella patens）的生殖细胞分化阶段活性显著升高。我们的实验数据表明，抑制ATG5介导的自噬会导致成熟卵细胞周围的卵细胞源性黏液密度降低，这提示自噬可能在细胞外黏液形成中发挥潜在功能。此外，我们发现ATG5与ATG7介导的自噬对于带鞭毛的可运动精子的分化及细胞质缩减过程不可或缺，进而直接影响精子的受精能力。苔藓与小鼠精子分化对巨自噬的需求存在惊人的相似性，这强烈表明自噬的祖先功能不仅限于抵御营养胁迫，同时还参与配子分化过程。

搜集汇总

背景与挑战

背景概述

该数据集研究了自噬在苔藓植物小立碗藓配子分化中的关键作用，发现ATG5和ATG7介导的自噬过程对卵细胞黏液形成和精子分化及生育力至关重要。数据集发布于2017年，涉及细胞生物学、植物生物学等领域，强调了自噬在植物配子发育中的进化保守功能。