Key Laboratory of Urban Agriculture (South), Ministry of Agriculture, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China.
Int J Mol Sci. 2022 Oct 11;23(20):12073. doi: 10.3390/ijms232012073.
Phosphate (Pi) deficiency is a common phenomenon in agricultural production and limits plant growth. Recent work showed that long-term Pi deficiency caused the inhibition of photosynthesis and inefficient electron transport. However, the underlying mechanisms are still unknown. In this study, we used the physiological, histochemical, and transcriptomic methods to investigate the effect of low-Pi stress on photosynthetic gas exchange parameters, cell membrane lipid, chloroplast ultrastructure, and transcriptional regulation of key genes in melon seedlings. The results showed that Pi deficiency significantly downregulated the expression of aquaporin genes, induced an increase in ABA levels, and reduced the water content and free water content of melon leaves, which caused physiological drought in melon leaves. Therefore, gas exchange was disturbed. Pi deficiency also reduced the phospholipid contents in leaf cell membranes, caused the peroxidation of membrane lipids, and destroyed the ultrastructure of chloroplasts. The transcriptomic analysis showed that 822 differentially expressed genes (DEGs) were upregulated and 1254 downregulated by Pi deficiency in leaves. GO and KEGG enrichment analysis showed that DEGs significantly enriched in chloroplast thylakoid membrane composition (GO:0009535), photosynthesis-antenna proteins (map00196), and photosynthesis pathways (map00195) were downregulated by Pi deficiency. It indicated that Pi deficiency regulated photosynthesis-related genes at the transcriptional level, thereby affecting the histochemical properties and physiological functions, and consequently causing the reduced light assimilation ability and photosynthesis efficiency. It enriches the mechanism of photosynthesis inhibition by Pi deficiency.
磷（Pi）缺乏是农业生产中的常见现象，限制了植物的生长。最近的研究表明，长期 Pi 缺乏会抑制光合作用和电子传递效率低下。然而，其潜在的机制仍不清楚。在这项研究中，我们使用生理、组织化学和转录组学方法来研究低 Pi 胁迫对甜瓜幼苗光合作用气体交换参数、细胞膜脂质、叶绿体超微结构和关键基因转录调控的影响。结果表明，Pi 缺乏显著下调水通道蛋白基因的表达，诱导 ABA 水平升高，降低甜瓜叶片的水分含量和游离水含量，导致甜瓜叶片发生生理性干旱，从而扰乱气体交换。Pi 缺乏还降低了叶细胞膜中的磷脂含量，导致膜脂过氧化，并破坏了叶绿体的超微结构。转录组分析表明，Pi 缺乏在叶片中上调了 822 个差异表达基因（DEGs），下调了 1254 个 DEGs。GO 和 KEGG 富集分析表明，DEGs 显著富集在叶绿体类囊体膜组成（GO：0009535）、光合作用天线蛋白（map00196）和光合作用途径（map00195），这表明 Pi 缺乏下调了与光合作用相关的基因。这表明 Pi 缺乏在转录水平上调节光合作用相关基因，从而影响组织化学特性和生理功能，进而导致光吸收能力和光合作用效率降低。这丰富了 Pi 缺乏抑制光合作用的机制。
