National Demonstration Center for Experimental Crop Science Education, College of Agronomy, Sichuan Agricultural University, Chengdu 611130, China.
State Key Laboratory of Crop Gene Exploration and Utilization in Southwest China, Sichuan Agricultural University, Chengdu 611130, China.
Int J Mol Sci. 2022 Apr 20;23(9):4518. doi: 10.3390/ijms23094518.
Starch phosphorylase (PHO) is a multimeric enzyme with two distinct isoforms: plastidial starch phosphorylase (PHO1) and cytosolic starch phosphorylase (PHO2). PHO1 specifically resides in the plastid, while PHO2 is found in the cytosol. Both play a critical role in the synthesis and degradation of starch. This study aimed to report the detailed structure, function, and evolution of genes encoding PHO1 and PHO2 and their protein ligand-binding sites in eight monocots and four dicots. "True" orthologs of PHO1 and PHO2 of were identified, and the structure of the enzyme at the protein level was studied. The genes controlling PHO2 were found to be more conserved than those controlling PHO1; the variations were mainly due to the variable sequence and length of introns. Cis-regulatory elements in the promoter region of both genes were identified, and the expression pattern was analyzed. The real-time quantitative polymerase chain reaction indicated that PHO2 was expressed in all tissues with a uniform pattern of transcripts, and the expression pattern of PHO1 indicates that it probably contributes to the starch biosynthesis during seed development in . Under abscisic acid (ABA) treatment, PHO1 was found to be downregulated in and However, we found that ABA could up-regulate the expression of both PHO1 and PHO2 within 12 h in . In all monocots and dicots, the 3D structures were highly similar, and the ligand-binding sites were common yet fluctuating in the position of aa residues.
淀粉磷酸化酶（PHO）是一种具有两种不同同工型的多聚体酶：质体淀粉磷酸化酶（PHO1）和细胞质淀粉磷酸化酶（PHO2）。PHO1 特异性位于质体中，而 PHO2 存在于细胞质中。两者在淀粉的合成和降解中都起着关键作用。本研究旨在报道 8 种单子叶植物和 4 种双子叶植物中编码 PHO1 和 PHO2 的基因的详细结构、功能和进化及其蛋白配体结合位点。鉴定了 的“真正”PHO1 和 PHO2 同源物，并研究了酶在蛋白质水平上的结构。发现控制 PHO2 的基因比控制 PHO1 的基因更保守；变异主要是由于内含子的可变序列和长度。鉴定了两个基因启动子区的顺式调控元件，并分析了其表达模式。实时定量聚合酶链反应表明，PHO2 在所有组织中均有表达，转录本的表达模式均匀，而 PHO1 的表达模式表明，它可能在种子发育过程中有助于淀粉的生物合成。在脱落酸（ABA）处理下，发现 PHO1 在 和 中下调。然而，我们发现 ABA 可以在 12 小时内上调 PHO1 和 PHO2 的表达。在所有单子叶植物和双子叶植物中，3D 结构高度相似，配体结合位点常见但 aa 残基的位置波动。
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