State Key Laboratory of Crop Genetics and Germplasm Enhancement, Cotton Germplasm Enhancement and Application Engineering Research Center (Ministry of Education), Nanjing Agricultural University, Nanjing, 210095, China.
BMC Plant Biol. 2022 Jul 22;22(1):357. doi: 10.1186/s12870-022-03748-w.
In eudicots, germination begins with water uptake by the quiescent dry seed and is greatly related to the permeability of micropyle enriched callose layers. Once imbibition starts, seeds undergo a cascade of physiological, biochemical, and molecular events to initiate cellular activities. However, the effects of callose on water uptake and following seed metabolic events during germination are largely unknown. Cotton (Gossypium hirsutum) is a eudicot plant with natural fiber and edible oil production for humans. Here, we addressed this question by examining the role of GhGLU19, a gene encoding β-1,3-glucanase, in cotton seed germination.
GhGLU19 belongs to subfamily B and was expressed predominately in imbibed seeds and early seedlings. Compared to wild type, GhGLU19-suppressing and GhGLU19-overexpressing transgenic cotton lines showed the higher and lower seed germination percentage, respectively. Callose was enriched more at inner integument (ii) than that in embryo and seed coat in cotton seeds. In GhGLU19-suppressing lines, callose at ii of cotton seeds was greatly increased and brought about a prolonged water uptake process during imbibition. Both proteomic and transcriptomic analysis revealed that contrary to GhGLU19-overexpressing lines, the glycolysis and pyruvate metabolism was decreased, and abscisic acid (ABA) biosynthesis related genes were downregulated in imbibed seeds of GhGLU19-suppressing lines. Also, endogenous ABA was significantly decreased in GhGLU19-suppressing line while increased in GhGLU19-overexpressing line.
Our results demonstrate that suppression of GhGLU19 improves cotton seed germination via accumulating callose of inner integument, modulating glycolysis and pyruvate metabolism, and decreasing ABA biosynthesis. This study provides a potential way for improving germination percentage in cotton seed production, and other eudicot crops.
在真双子叶植物中，种子的萌发始于休眠干燥种子对水分的吸收，并且与富含胼胝质的珠孔层的通透性密切相关。一旦开始吸水，种子就会经历一系列生理、生化和分子事件，从而启动细胞活动。然而，关于胼胝质对吸水以及随后萌发过程中种子代谢事件的影响在很大程度上仍是未知的。棉花（Gossypium hirsutum）是一种真双子叶植物，可用于生产人类用的天然纤维和食用油。在这里，我们通过研究编码β-1,3-葡聚糖酶的 GhGLU19 基因在棉花种子萌发中的作用来回答这个问题。
GhGLU19 属于亚家族 B，在吸胀种子和早期幼苗中表达量较高。与野生型相比，GhGLU19 抑制和 GhGLU19 过表达转基因棉花系的种子萌发率分别较高和较低。在棉花种子中，内种皮（ii）的胼胝质比胚和种皮中的更丰富。在 GhGLU19 抑制系中，棉花种子的 ii 中的胼胝质大量增加，导致在吸胀过程中吸水过程延长。蛋白质组学和转录组学分析表明，与 GhGLU19 过表达系相反，GhGLU19 抑制系中的糖酵解和丙酮酸代谢降低，并且内源性 ABA 显著减少，而 GhGLU19 过表达系中的 ABA 生物合成相关基因下调。
我们的结果表明，通过积累内种皮的胼胝质、调节糖酵解和丙酮酸代谢以及降低 ABA 生物合成，抑制 GhGLU19 可提高棉花种子的萌发率。本研究为提高棉花种子生产和其他真双子叶作物的萌发率提供了一种潜在的方法。
