This study investigated the role of the sugar transporter OsSWEET11 during the early stage of rice caryopsis development using β-glucoronidase (GUS) to represent its expression, together with clustered regularly interspaced short palindromic repeats–CRISPR-associated protein 9 (CRISPR–Cas9)-mediated knockout, cross-fertilization and RNA sequencing (RNA-seq) analyses. The results showed that OsSWEET11 was expressed strongly in developing caryopsis, particularly in the ovular vascular trace, nucellar epidermis and cross cells. The knockout of OsSWEET11 significantly decreased the sucrose concentration in the mutant embryo sacs and led to defective grain filling compared with that of the wild-type (WT) plant. Moreover, the expression of 2,549 genes in the mutant caryopsis was affected. The grain weight and seed setting percentage were also decreased in the mutants. The cross-fertilization of the mutant and WT rice revealed that the mutated maternal donor induced defective grain filling. These results strongly suggested that OsSWEET11 played an important role in sucrose release from maternal tissue to the maternal–filial interface during the early stage of caryopsis development. It might also induce sucrose release from the ovular vascular trace and cross cells of developing caryopsis. These findings bridge the gap in the understanding of post-phloem sugar transport during the early stage of rice caryopsis development.
本研究以β-葡萄糖醛酸酶（GUS）為表達(dá)載體，結(jié)合成簇規(guī)律間隔短回文重復(fù)序列CRISPR相關(guān)蛋白9（CRISPR–Cas9）介導(dǎo)的敲除、雜交試驗(yàn)和RNA測序（RNA-seq）分析，研究了糖轉(zhuǎn)運(yùn)蛋白OsSWEET11在水稻穎果發(fā)育早期的作用。結(jié)果表明，OsSWEET11在穎果發(fā)育過程中有較強(qiáng)的表達(dá)，特別是在胚珠的維管束、珠心表皮和橫細(xì)胞中。與野生型相比，OsSWEET11基因敲除顯著降低了突變體胚囊中的蔗糖濃度，導(dǎo)致籽粒灌漿缺陷。此外，突變體穎果中2549個(gè)基因的表達(dá)也受到影響。突變體的粒重和結(jié)實(shí)率也有所下降。突變體與野生型的雜交試驗(yàn)表明，突變體的母體供體誘導(dǎo)了籽粒灌漿缺陷。這些結(jié)果有力地表明，在穎果發(fā)育的早期階段，OsSWEET11在從母體組織向母子界面的蔗糖釋放中起著重要的作用。它還可能誘導(dǎo)穎果發(fā)育過程中胚珠維管束和橫細(xì)胞釋放蔗糖。這些發(fā)現(xiàn)填補(bǔ)了人們對水稻穎果發(fā)育早期韌皮部之后的糖轉(zhuǎn)運(yùn)認(rèn)識上的空白。