Background

The Glucan synthase-like (GSL) genes are indispensable for some important highly-specialized developmental and cellular processes involving callose synthesis and deposition in plants. At present, the best-characterized reproductive functions of GSL genes are those for pollen formation and ovary expansion, but their role in seed initiation remains unknown.

Results

We identified a rice seed mutant, watery seed 1-1 (ws1-1), which contained a mutation in the OsGSL2 gene. The mutant produced seeds lacking embryo and endosperm but filled with transparent and sucrose-rich liquid. In a ws1-1 spikelet, the ovule development was normal, but the microsporogenesis and male gametophyte development were compromised, resulting in the reduction of fertile pollen. After fertilization, while the seed coat normally developed, the embryo failed to differentiate normally. In addition, the divided endosperm-free nuclei did not migrate to the periphery of the embryo sac but aggregated so that their proliferation and cellularization were arrested. Moreover, the degeneration of nucellus cells was delayed in ws1-1. OsGSL2 is highly expressed in reproductive organs and developing seeds. Disrupting OsGSL2 reduced callose deposition on the outer walls of the microspores and impaired the formation of the annular callose sheath in developing caryopsis, leading to pollen defect and seed abortion.

Conclusions

Our findings revealed that OsGSL2 is essential for rice fertility and is required for embryo differentiation and endosperm-free nucleus positioning, indicating a distinct role of OsGSL2, a callose synthase gene, in seed initiation, which provides new insight into the regulation of seed development in cereals.

中文翻译：

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类葡聚糖合酶 2 是水稻种子萌发、灌浆以及花粉育性所必需的

背景

类葡聚糖合酶( GSL )基因对于一些重要的高度专业化的发育和细胞过程（涉及植物中的胼胝质合成和沉积）是不可或缺的。目前， GSL基因最具代表性的生殖功能是花粉形成和子房扩张，但它们在种子起始中的作用仍不清楚。

结果

我们鉴定了一种水稻种子突变体，水种子 1-1 ( ws1-1 )，其中包含OsGSL2基因突变。该突变体产生的种子缺乏胚和胚乳，但充满透明且富含蔗糖的液体。在ws1-1小穗中，胚珠发育正常，但小孢子发生和雄配子体发育受到损害，导致可育花粉减少。受精后，虽然种皮正常发育，但胚胎未能正常分化。此外，分裂的无胚乳核不会迁移到胚囊的外围，而是聚集，从而抑制了它们的增殖和细胞化。此外， ws1-1中珠心细胞的变性被延迟。OsGSL2在生殖器官和发育中的种子中高度表达。破坏OsGSL2会减少小孢子外壁上的胼胝质沉积，并损害发育中的颖果中环形胼胝质鞘的形成，导致花粉缺陷和种子败育。

结论

我们的研究结果表明，OsGSL2对于水稻育性至关重要，并且是胚胎分化和无胚乳核定位所必需的，这表明OsGSL2（一种胼胝质合酶基因）在种子起始中的独特作用，这为水稻种子发育的调控提供了新的见解。谷物。