Background Saline-alkaline stress is a major abiotic stress that is harmful to plant growth worldwide. Two peach cultivars (GF677 and Maotao) display distinct phenotypes under saline-alkaline stress. The molecular mechanism explaining the differences between the two cultivars is still unclear. Results In the present study, we systematically analysed the changes in GF677 and Maotao leaves upon saline-alkaline stress by using cytological and biochemical technologies as well as comparative transcriptome analysis. Transmission electron microscopy (TEM) observations showed that the structure of granum was dispersive in Maotao chloroplasts. The biochemical analysis revealed that POD activity and the contents of chlorophyll a and chlorophyll b, as well as iron, were notably decreased in Maotao. Comparative transcriptome analysis detected 881 genes with differential expression (including 294 upregulated and 587 downregulated) under the criteria of |log2 Ratio| ≥ 1 and FDR ≤0.01. Gene ontology (GO) analysis showed that all differentially expressed genes (DEGs) were grouped into 30 groups. MapMan annotation of DEGs showed that photosynthesis, antioxidation, ion metabolism, and WRKY TF were activated in GF677, while cell wall degradation, secondary metabolism, starch degradation, MYB TF, and bHLH TF were activated in Maotao. Several iron and stress-related TFs ( ppa024966m , ppa010295m , ppa0271826m , ppa002645m , ppa010846m , ppa009439m , ppa008846m , and ppa007708m ) were further discussed from a functional perspective based on the phylogenetic tree integration of other species homologues. Conclusions According to the cytological and molecular differences between the two cultivars, we suggest that the integrity of chloroplast structure and the activation of photosynthesis as well as stress-related genes are crucial for saline-alkaline resistance in GF677. The results presented in this report provide a theoretical basis for cloning saline-alkaline tolerance genes and molecular breeding to improve saline-alkaline tolerance in peach.

中文翻译：

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比较转录组分析揭示了盐碱胁迫下两个桃品种之间的基因表达差异

背景盐碱胁迫是一种主要的非生物胁迫，对世界范围内的植物生长有害。两个桃品种（GF677 和茅桃）在盐碱胁迫下表现出不同的表型。解释这两个品种之间差异的分子机制仍不清楚。结果在本研究中，我们利用细胞学和生化技术以及比较转录组分析系统地分析了GF677和茅桃叶片在盐碱胁迫下的变化。透射电子显微镜 (TEM) 观察表明颗粒结构分散在茅桃叶绿体中。生化分析表明，茅桃的POD活性、叶绿素a和叶绿素b含量以及铁含量均显着降低。比较转录组分析在|log2 Ratio|标准下检测到881个差异表达基因（包括294个上调和587个下调）。≥ 1 且 FDR ≤0.01。基因本体（GO）分析显示，所有差异表达基因（DEG）分为30组。DEGs的MapMan注释显示GF677激活了光合作用、抗氧化、离子代谢和WRKY TF，而毛桃激活了细胞壁降解、次级代谢、淀粉降解、MYB TF和bHLH TF。几个铁和压力相关的 TF（ ppa024966m , ppa010295m , ppa0271826m , ppa002645m , ppa010846m , ppa009439m , ppa008846m , 和 ppa007708 的其他功能物种是从其他基因系统整合的角度进一步讨论的）。结论 根据两个品种间的细胞学和分子差异，我们认为叶绿体结构的完整性和光合作用的激活以及胁迫相关基因对GF677的盐碱抗性至关重要。本报告的研究结果为克隆耐盐碱基因和分子育种提高桃耐盐碱性提供了理论依据。