College of Horticulture, Shanxi Agricultural University, Taigu, Shanxi, P. R. China.
Shanxi Key Laboratory of Germplasm Improvement and Utilization in Pomology, Taigu, Shanxi, P. R. China.
PLoS One. 2018 Apr 26;13(4):e0196537. doi: 10.1371/journal.pone.0196537. eCollection 2018.
Cerasus humilis (Bge.) Sok and Cerasus glandulosa (Thunb.) Lois are economically important fruit-producing shrubs. Although these two species have similar looking fruits, their fruit organic acid contents differ drastically. In this study, we focused on comparing the organic acid content, activity of enzymes gene expression involved in organic acid metabolism in both C. humilis and C. glandulosa fruits. To investigate the differences of organic acid metabolism in fruits of these two species, a comparative transcriptome analysis was performed. Our results showed that temporal changes of two main organic acids exhibited different trends in these two species. Transcriptome sequencing of developing C. humilis and C. glandulosa fruits systematically revealed 6,594 differentially expressed genes. Compared with C. humilis, the expression levels of 3,469 and 3,125 genes were up- and down-regulated in C. glandulosa, respectively, including one PEPC gene, 12 malic acid metabolism genes, 25 citric acid cycle genes, and 194 NAD/NADP metabolism genes. The correlation analysis and principal component analysis of gene expression, enzymatic activity and organic acid content showed that differences in the expression of genes encoding the NAD-malate dehydrogenase (NAD-MDH) and NADP-malate enzyme (NADP-ME) contributed substantially to the observed differences in organic acid accumulation of two species. Our results provide a solid foundation for future elucidation of key mechanisms regulating organic acid biosynthesis in C. humilis and C. glandulosa fruits and could lead to efficient and highly targeted generation of more commercially accepted cultivars.
矮樱（Bge.）和腺肋樱（Thunb.）是经济上重要的产果灌木。尽管这两个物种的果实外观相似，但它们的果实有机酸含量却有很大的不同。在这项研究中，我们专注于比较这两个物种果实中的有机酸含量、参与有机酸代谢的酶的活性和基因表达。为了研究这两个物种果实中有机酸代谢的差异，我们进行了比较转录组分析。我们的结果表明，两种主要有机酸的时间变化在这两个物种中呈现出不同的趋势。对发育中的矮樱和腺肋樱果实进行转录组测序，系统地揭示了 6594 个差异表达基因。与矮樱相比，腺肋樱中有 3469 个和 3125 个基因的表达水平上调和下调，分别包括一个 PEPC 基因、12 个苹果酸代谢基因、25 个柠檬酸循环基因和 194 个 NAD/NADP 代谢基因。基因表达、酶活性和有机酸含量的相关分析和主成分分析表明，编码 NAD-苹果酸脱氢酶（NAD-MDH）和 NADP-苹果酸酶（NADP-ME）的基因表达差异是导致这两个物种有机酸积累差异的主要原因。我们的研究结果为进一步阐明矮樱和腺肋樱果实中有机酸生物合成的关键机制提供了坚实的基础，并可能导致更高效、更有针对性地产生更受商业欢迎的品种。
