Agricultural Biotechnology Research Center, Academia Sinica, Taipei, Taiwan.
Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
Plant Physiol. 2023 Jan 2;191(1):177-198. doi: 10.1093/plphys/kiac494.
Phosphoglucose isomerase (PGI) catalyzes the interconversion of fructose-6-phosphate and glucose-6-phosphate, which impacts cell carbon metabolic flow. Arabidopsis (Arabidopsis thaliana) contains two nuclear PGI genes respectively encoding plastidial PGI1 and cytosolic PGI (cPGI). The loss of PGI1 impairs the conversion of F6P of the Calvin-Benson cycle to G6P for the synthesis of transitory starch in leaf chloroplasts. Since cpgi knockout mutants have not yet been obtained, they are thought to be lethal. The cpgi lethality can be rescued by expressing CaMV 35S promoter (p35S)-driven cPGI; however, the complemented line is completely sterile due to pollen degeneration. Here, we generated a cpgi mutant expressing p35S::cPGI-YFP in which YFP fluorescence in developing anthers was undetectable specifically in the tapetum and in pollen, which could be associated with male sterility. We also generated RNAi-cPGI knockdown lines with strong cPGI repression in floral buds that exhibited reduced male fertility due to the degeneration of most pollen. Histological analyses indicated that the synthesis of intersporal callose walls was impaired, causing microsporocytes to fail to separate haploid daughter nuclei to form tetrads, which might be responsible for subsequent pollen degeneration. We successfully isolated cpgi knockout mutants in the progeny of a heterozygous cpgi mutant floral-dipped with sugar solutions. The rescued cpgi mutants exhibited diminished young vegetative growth, reduced female fertility, and impaired intersporal callose wall formation in a meiocyte, and, thus, male sterility. Collectively, our data suggest that cPGI plays a vital role in carbohydrate partitioning, which is indispensable for microsporogenesis and early embryogenesis.
磷酸葡萄糖异构酶（PGI）催化果糖-6-磷酸和葡萄糖-6-磷酸的相互转化，从而影响细胞碳代谢流。拟南芥（Arabidopsis thaliana）含有两个核 PGI 基因，分别编码质体 PGI1 和细胞质 PGI（cPGI）。PGI1 的缺失会损害卡尔文-本森循环的 F6P 向叶绿体质体中转瞬即逝淀粉合成的 G6P 转化。由于尚未获得 cpgi 敲除突变体，因此认为它们是致命的。通过表达 CaMV 35S 启动子（p35S）驱动的 cPGI 可以挽救 cpgi 致死性；然而，由于花粉退化，互补系是完全不育的。在这里，我们生成了一个在发育中的花药中特异性地在绒毡层和花粉中检测不到 YFP 荧光的 p35S::cPGI-YFP 表达的 cpgi 突变体，这可能与雄性不育有关。我们还生成了具有强烈 cPGI 抑制作用的 RNAi-cPGI 敲低系，这些系由于大多数花粉退化而导致雄性育性降低。组织学分析表明，间质 Callose 壁的合成受到损害，导致小孢子母细胞无法分离单倍体细胞核形成四分体，这可能是导致随后花粉退化的原因。我们成功地从一个杂合 cpgi 突变体的后代中分离出 cpgi 敲除突变体，该突变体在花上蘸糖溶液。 rescued cpgi 突变体表现出生长减缓、雌性育性降低以及减数分裂中间质 Callose 壁形成受损，从而导致雄性不育。总之，我们的数据表明 cPGI 在碳水化合物分配中起着至关重要的作用，这对于小孢子发生和早期胚胎发生是必不可少的。
