College of Horticulture, Gansu Agricultural University, Lanzhou, 730070, PR China.
BMC Plant Biol. 2024 May 8;24(1):374. doi: 10.1186/s12870-024-05069-6.
PC (phytocyanin) is a class of copper-containing electron transfer proteins closely related to plant photosynthesis, abiotic stress responses growth and development in plants, and regulation of the expression of some flavonoids and phenylpropanoids, etc., however, compared with other plants, the PC gene family has not been systematically characterized in apple.
A total of 59 MdPC gene members unevenly distributed across 12 chromosomes were identified at the genome-wide level. The proteins of the MdPC family were classified into four subfamilies based on differences in copper binding sites and glycosylation sites: Apple Early nodulin-like proteins (MdENODLs), Apple Uclacyanin-like proteins (MdUCLs), Apple Stellacyanin-like proteins (MdSCLs), and Apple Plantacyanin-like proteins (MdPLCLs). Some MdPC members with similar gene structures and conserved motifs belong to the same group or subfamily. The internal collinearity analysis revealed 14 collinearity gene pairs among members of the apple MdPC gene. Interspecific collinearity analysis showed that apple had 31 and 35 homologous gene pairs with strawberry and grape, respectively. Selection pressure analysis indicated that the MdPC gene was under purifying selection. Prediction of protein interactions showed that MdPC family members interacted strongly with the Nad3 protein. GO annotation results indicated that the MdPC gene also regulated the biosynthesis of phenylpropanoids. Chip data analysis showed that (MdSCL3, MdSCL7 and MdENODL27) were highly expressed in mature fruits and peels. Many cis-regulatory elements related to light response, phytohormones, abiotic stresses and flavonoid biosynthetic genes regulation were identified 2000 bp upstream of the promoter of the MdPC gene, and qRT-PCR results showed that gene members in Group IV (MdSCL1/3, MdENODL27) were up-regulated at all five stages of apple coloring, but the highest expression was observed at the DAF13 (day after fruit bag removal) stage. The gene members in Group II (MdUCL9, MdPLCL3) showed down-regulated or lower expression in the first four stages of apple coloring but up-regulated and highest expression in the DAF 21 stage.
Herein, one objective of these findings is to provide valuable information for understanding the structure, molecular evolution, and expression pattern of the MdPC gene, another major objective in this study was designed to lay the groundwork for further research on the molecular mechanism of PC gene regulation of apple fruit coloration.
PC（藻蓝蛋白）是一类与植物光合作用、非生物胁迫响应、生长发育以及某些类黄酮和苯丙烷类物质表达调控等密切相关的含铜电子传递蛋白。然而，与其他植物相比，PC 基因家族在苹果中尚未得到系统的描述。
在全基因组水平上，共鉴定到 59 个不均匀分布在 12 条染色体上的 MdPC 基因成员。根据铜结合位点和糖基化位点的差异，将 MdPC 家族蛋白分为四个亚家族：苹果早期结瘤素样蛋白（MdENODLs）、苹果 Uclacyanin 样蛋白（MdUCLs）、苹果 Stellacyanin 样蛋白（MdSCLs）和苹果 Plantacyanin 样蛋白（MdPLCLs）。一些具有相似基因结构和保守基序的 MdPC 成员属于同一组或亚家族。内部共线性分析显示，苹果 MdPC 基因成员中有 14 对共线性基因对。种间共线性分析表明，苹果与草莓和葡萄分别有 31 对和 35 对同源基因对。选择压力分析表明，MdPC 基因受到纯化选择。蛋白质相互作用预测表明，MdPC 家族成员与 Nad3 蛋白相互作用强烈。GO 注释结果表明，MdPC 基因还调控苯丙烷类物质的生物合成。芯片数据分析表明，（MdSCL3、MdSCL7 和 MdENODL27）在成熟果实和果皮中高表达。在 MdPC 基因启动子上游 2000bp 处鉴定到与光响应、植物激素、非生物胁迫和类黄酮生物合成基因调控相关的许多顺式调控元件，qRT-PCR 结果表明，第 IV 组（MdSCL1/3、MdENODL27）的基因成员在苹果着色的所有五个阶段均上调，但在 DAF13（果实去袋后天数）阶段表达最高。第 II 组（MdUCL9、MdPLCL3）的基因成员在苹果着色的前四个阶段下调或低表达，但在 DAF21 阶段上调且表达最高。
本研究的一个目的是为了解 MdPC 基因的结构、分子进化和表达模式提供有价值的信息，另一个主要目的是为进一步研究 PC 基因调控苹果果实着色的分子机制奠定基础。
