Zhang Shuhui, Peng Futian, Xiao Yuansong, Wang Wenru, Wu Xuelian
State Key Laboratory of Crop Biology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, China.
Front Plant Sci. 2020 Apr 24;11:409. doi: 10.3389/fpls.2020.00409. eCollection 2020.
Sugar signals play a key role in root growth and development. SnRK1, as one of the energy centers, can respond to energy changes in plants and affect the growth and development of plants. However, studies on sugar signals and SnRK1 regulating root growth in fruit trees have not been reported. In this study, we found that 5% exogenous sucrose could increase the total volume and total surface area of the peach root system, enhance the number and growth of lateral roots, and promote the activity of SnRK1. When exogenous trehalose was applied, the growth of roots was poor. Sucrose treatment reversed the inhibitory effects of trehalose on SnRK1 enzyme activity and root growth. We also found that the lateral root number of -overexpressing plants (4-1, 4-2, and 4-3) increased significantly. Therefore, we believe that peach SnRK1 is involved in sucrose-mediated root growth and development. To further clarify this mechanism, we used qRT-PCR analysis to show that exogenous sucrose could promote the expression of auxin-related genes in roots, thereby leading to the accumulation of auxin in the root system. In addition, the genes related to auxin synthesis and auxin transport in the root systems of -overexpressing lines were also significantly up-regulated. Using peach PpSnRK1a as the bait, we obtained two positive clones, PpIAA12 and PpPIN-LIKES6, which play key roles in auxin signaling. The interactions between peach PpSnRK1a and PpIAA12/PpPIN-LIKES6 were verified by yeast two-hybrid assays and bimolecular fluorescence complementation experiments, and the complexes were localized in the nucleus. After exogenous trehalose treatment, the expression of these two genes in peach root system was inhibited, whereas sucrose had a significant stimulatory effect and could alleviate the inhibition of these two genes by trehalose, which was consistent with the trend of sucrose's regulation of SnRK1 activity. In conclusion, peach SnRK1 can respond to sucrose and regulate root growth through the auxin signal pathway. This experiment increases our understanding of the function of fruit tree SnRK1 and provides a new insight to further study sugar hormone crosstalk in the future.
糖信号在根系生长发育中起关键作用。SnRK1作为能量中心之一，能够响应植物体内的能量变化并影响植物的生长发育。然而，关于糖信号和SnRK1调控果树根系生长的研究尚未见报道。在本研究中，我们发现5%的外源蔗糖可增加桃根系的总体积和总表面积，增强侧根数量和生长，并促进SnRK1的活性。施加外源海藻糖时，根系生长较差。蔗糖处理可逆转海藻糖对SnRK1酶活性和根系生长的抑制作用。我们还发现过表达植株（4-1、4-2和4-3）的侧根数量显著增加。因此，我们认为桃SnRK1参与蔗糖介导的根系生长发育。为进一步阐明该机制，我们通过qRT-PCR分析表明外源蔗糖可促进根系中生长素相关基因的表达，从而导致根系中生长素的积累。此外，过表达株系根系中与生长素合成和生长素运输相关的基因也显著上调。以桃PpSnRK1a为诱饵，我们获得了两个在生长素信号传导中起关键作用的阳性克隆PpIAA12和PpPIN-LIKES6。通过酵母双杂交试验和双分子荧光互补实验验证了桃PpSnRK1a与PpIAA12/PpPIN-LIKES6之间的相互作用，且复合物定位于细胞核。外源海藻糖处理后，桃根系中这两个基因的表达受到抑制，而蔗糖具有显著的促进作用，并可缓解海藻糖对这两个基因的抑制，这与蔗糖对SnRK1活性的调控趋势一致。总之，桃SnRK1可响应蔗糖并通过生长素信号通路调控根系生长。本实验增进了我们对果树SnRK1功能的理解，并为未来进一步研究糖激素互作提供了新的见解。
