College of Horticulture, China Agricultural University, Beijing, China.
State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, China.
Plant Cell Environ. 2019 Feb;42(2):424-436. doi: 10.1111/pce.13403. Epub 2018 Oct 2.
Plants experiencing salt-induced stress often reduce cytokinin levels during the early phases of stress-response. Interestingly, we found that the cytokinin content in the apple rootstock "robusta" was maintained at a high level under salt stress. Through screening genes involved in cytokinin biosynthesis and catabolism, we found that the high expression levels of IPT5b in robusta roots were involved in maintaining the high cytokinin content. We identified a 42 bp deletion in the promoter region of IPT5b, which elevated IPT5b expression levels, and this deletion was linked to salt tolerance in robusta×M.9 segregating population. The 42 bp deletion resulted in the deletion of a Proline Response Element (ProRE), and our results suggest that ProRE negatively regulates IPT5b expression in response to proline. Under salt stress, the robusta cultivar maintains high cytokinin levels as IPT5b expression cannot be inhibited by proline due to the deletion of ProRE, leading to improve salt tolerance.
在受到盐胁迫的早期阶段，植物通常会降低细胞分裂素水平。有趣的是，我们发现苹果砧木“健壮”在盐胁迫下细胞分裂素含量保持在高水平。通过筛选参与细胞分裂素生物合成和分解代谢的基因，我们发现健壮根系中 IPT5b 的高表达水平参与维持高细胞分裂素含量。我们在 IPT5b 的启动子区域鉴定出一个 42bp 的缺失，该缺失导致 IPT5b 表达水平升高，并且该缺失与健壮×M.9 分离群体的耐盐性有关。42bp 的缺失导致一个脯氨酸反应元件（ProRE）的缺失，我们的结果表明 ProRE 负调控 IPT5b 的表达以响应脯氨酸。在盐胁迫下，由于 ProRE 的缺失，健壮品种不能被脯氨酸抑制 IPT5b 的表达，从而维持高水平的细胞分裂素，导致耐盐性提高。
