Key Laboratory of Silkworm and Mulberry Genetic Improvement, Ministry of Agriculture, School of Biology and Technology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China; Sericultural Research Institute, Anhui Academy of Agricultural Sciences, Hefei, Anhui, China.
Key Laboratory of Silkworm and Mulberry Genetic Improvement, Ministry of Agriculture, School of Biology and Technology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, China.
Plant Physiol Biochem. 2018 Nov;132:603-611. doi: 10.1016/j.plaphy.2018.10.007. Epub 2018 Oct 9.
Shaggy-like protein kinase (SK) plays important roles in the plant growth development, signal transduction, abiotic stress and biotic stress and substance metabolism regulation. However, the exact function of the response to drought stress in mulberry with SK remains unclear. In this study, a new SK gene that was designated as MmSK (GenBank accession NO: KY348867) was isolated and cloned from mulberry (Morus alba). MmSK contains two SK conservation domains of ATP domain and Serine/Threonine protein kinases active-site signature, and belonged to GSK3/shaggy protein kinase family. The expression of MmSK in mulberry was up-regulated under various abiotic stress treatments. Meanwhile, we observed higher expression levels in the phloem contrasted with other tissues. Mulberry MmSK gene was successfully silenced by virus induced gene silencing (VIGS), and after MmSK was silenced, the expression of MmSK in pTRV2-MmSK-VIGS plant (transgenic mulberry) dropped to 34.02% compared with the negative control inoculated with empty vector pTRV2-00 (CK). Under drought stress, the soluble protein content, proline content, superoxide dismutase (SOD) and peroxidase (POD) activities in transgenic mulberry decreased in different degree compared with the CK. In contrast, the accumulation of malondialdehyde (MDA) increased significantly in transgenic mulberry. With the extension of drought stress treatment time, the soluble protein content, proline content and MDA content gradually increased. The SOD activity and POD activity under drought stress gradually rose to the maximum on the fifth day and then decreased, which consistent with the change trend of MmSK gene expression. These results suggested that MmSK gene could function as a positive regulator of drought stress in mulberry.
沙基样蛋白激酶（SK）在植物生长发育、信号转导、非生物胁迫和生物胁迫以及物质代谢调节中发挥重要作用。然而，桑树中 SK 对干旱胁迫响应的确切功能仍不清楚。本研究从桑树中分离并克隆了一个新的 SK 基因，命名为 MmSK（GenBank 登录号：KY348867）。MmSK 含有两个 SK 保守结构域，即 ATP 结构域和丝氨酸/苏氨酸蛋白激酶活性位点特征，属于 GSK3/沙基样蛋白激酶家族。MmSK 在桑树中的表达在各种非生物胁迫处理下上调。同时，我们观察到它在韧皮部的表达水平高于其他组织。通过病毒诱导的基因沉默（VIGS）成功沉默了桑树 MmSK 基因，沉默后，转 MmSK 基因的 pTRV2-MmSK-VIGS 植株（转基因桑树）中的 MmSK 表达量与接种空载体 pTRV2-00（CK）的阴性对照相比下降到 34.02%。在干旱胁迫下，与 CK 相比，转基因桑树中的可溶性蛋白含量、脯氨酸含量、超氧化物歧化酶（SOD）和过氧化物酶（POD）活性均有不同程度的降低。相反，丙二醛（MDA）的积累在转基因桑树中显著增加。随着干旱胁迫处理时间的延长，可溶性蛋白含量、脯氨酸含量和 MDA 含量逐渐增加。干旱胁迫下 SOD 活性和 POD 活性逐渐在第 5 天达到最大值，然后降低，与 MmSK 基因表达的变化趋势一致。这些结果表明，MmSK 基因可作为桑树干旱胁迫的正调控因子。
