钾离子在梨树砧穗间高效转运的生理与分子机制

Potassium is a key element that affects the yield and quality of pear. High efficient transport of potassium between rootstock and scion can lead to improvement of potassium absorption and utilization. In our previous studies, we found that PbHAK12 and PbAKT1 were high efficient potassium transporters in potassium absorption and transport. However, the physiological and molecular mechanism of high efficient transport of K+ between rootstock and scion of pear is still unknown. Pyrus ussuriensis and Pyrus betulaefolia was high K efficiency genotype and low K efficiency genotype, respectively. In this project, the autologous grafting and heterogeneous grafting of these two cultivars will be used to study the tissue localization of the high efficient transporter genes between stock and scion of pear under potassium deficiency by the in-situ hybridization. The ring stripping technique blocking the material transport in phloem will be used to determine the characteristics of high K efficiency genes in the long distance transmission of phloem, so that we can reveal the mutual response to roots and above ground and clarify the physiological and molecular mechanism of K high efficient transport between rootstock and scion to improve potassium efficiency. Our project will enrich the grafting theory of fruit trees and the theory of mineral nutrition, promote pear rootstock breeding with low potassium tolerance and the development stocks and scions combinations, and provide the theoretical and practical foundation for improvig the quality and efficiency.

钾素是影响梨产量和品质的关键元素，砧穗间钾的高效运转可以显著改善梨树对钾素的吸收与利用，我们前期研究发现，钾离子转运体基因PbHAK12和PbAKT1是其响应外界供钾水平的高效吸收和转运基因，目前关于钾离子在砧穗间高效吸收和转运的生理与分子调控机制尚不清楚。本项目采用山梨和杜梨的自体嫁接和异体嫁接组合，通过原位杂交技术确定缺钾胁迫下钾高效基因在砧穗间的定位；采用环剥技术阻断韧皮部物质的运输，明确钾高效基因在砧穗间远距离传递特征，阐明嫁接组合中砧木对缺钾胁迫产生的响应在接穗中的传递以及接穗对砧木的反馈机制，揭示K+在梨树砧穗间高效运转和利用的生理与分子机制。本项目的研究结果将能丰富果树的嫁接理论和矿质营养学说，促进耐低钾砧木选育及钾高效砧穗组合技术开发，为提质增效提供理论依据和技术支撑。

在一年生山梨和杜梨为砧木的嫁接体系中，我们发现，以山梨为砧木的嫁接体在施钾条件下增加了地上部的生物量积累和钾的吸收及转运，可能与其促进韧皮部的发育、增加韧皮部厚度有关；以杜梨为砧木的嫁接体对低钾条件更为敏感。植物激素参与了这一生理过程，IAA、GA3和ZR可能促进了山梨地上部生长，而ABA和JA可能与杜梨抗逆性的增加有关。转录组结果表明，不同砧木影响了地上部基因的表达，主要通过代谢和抗逆途径来影响地上部的生长。通过环剥探究了钾转运基因PbAKT1、PbAKT2、PbSKOR在嫁接体中的表达，发现在钾高效品种山梨中其表达量相对较高。