甜高粱根质外体屏障栓质形成关键基因SbKCS11在拒盐中的作用机理研究

Sorghum bicolor (L.) Moench is a variation of traditional grain sorghum, a C4 crop, with the characteristics of high biomass and abiotic stress resistance. It is considered as the best material for the production of fuel ethanol. Sweet sorghum has developed a strategy to resist salinity by accumulating salt such as Na+ in the roots to limit the excess accumulation of Na+ in leaves under salt stress. However, the mechanism of salt exclusion in Sorghum bicolor is unknown. In this project, the function and the molecular mechanism of key genes related with suberin-forming key genes (SbKCS11) in salt exclusion of sweet sorghum will be explored. On one hand, salt-tolerant (M-81E) and salt-sensitive (Roma) sweet sorghum inbred lines will be used to elucidate the role of root suberin lamellae in salt exclusion by examining the growth, the ability of the root suberin lamellae in Na+ exclusion, expression and localization of the genes, changes in morphology and composition of suberin lamellae under salt stress. On the other hand, wild type, overexpression lines and knock-out mutants of sweet sorghum will be used to study the molecular mechanism of root suberin lamellae in salt exclusion by examining the growth, the ability of the root suberin lamellae in Na+ exclusion, expression and localization of the genes, changes in morphology and composition of suberin lamellae under salt stress.

甜高粱 [Sorghum bicolor (L.) Moench]是普通粒用高粱的一个变种，为C4作物，具有生物量高、抗逆性强的特点，被认为是生产燃料乙醇的最佳原料。甜高粱具有较强抗盐性，主要表现为根的拒Na+能力强，这使得其在盐胁迫下仍能保证叶片等地上部分较低的Na+含量，降低盐害。但是，甜高粱的拒Na+机理尚不清楚。本项目主要探讨根质外体屏障栓质层形成关键基因（SbKCS11）在甜高粱根拒Na+中的作用机理。一方面，利用前期已经筛选到的耐盐（M-81E）及盐敏感(Roma)甜高粱自交系，通过测定NaCl胁迫下生长、质外体屏障拒Na+能力、基因表达、定位及栓质层形态及成分等揭示栓质层参与甜高粱拒Na+的作用；另一方面，通过测定NaCl胁迫下甜高粱野生型、基因缺失突变体和过表达株系生长、质外体屏障拒Na+能力、基因表达、定位及栓质层形态及成分等揭示栓质层参与拒Na+的分子机理。

甜高粱[Sorghum bicolor (L.) Mocnch]， “粮食-经济-饲草”三元种植作物，具有耐盐碱、抗旱、耐涝等优良特性。本项目以耐盐甜高粱自交系M-81E和盐敏感自交系Roma为材料，探究了甜高粱拒Na+的作用机制，主要研究结果如下：（1）甜高粱拒盐性与质外体屏障密切相关，盐处理下M-81E与Roma根部内皮层质外体屏障（木质化和栓质化）均受到盐诱导而加厚，且前者的增厚程度更大，初步解释了M-81E的拒盐能力更强；（2）确定了甜高粱根质外体屏障发育模式及位置，根据凯氏带和栓质的形成情况，我们将M-81E与Roma质外体屏障的发育分为3个时期：Stage I（无凯氏带和栓质形成）、Stage II（凯氏带和栓质正在形成）和Stage III（凯氏带和栓质完全成熟）；（3）通过高通量转录组测序确定了甜高粱质外体屏障形成的相关基因，SbCASP4和SbCASP-LP1C1在盐处理后都出现较高表达，同时，结合原位杂交结果，表明这两个基因在甜高粱根内皮层处进行表达，进而证明其可能参与质外体屏障的发育过程；（4）SbCASP4和SbCASP-LP1C1及其启动子克隆及功能研究，通过在拟南芥中异源表达SbCASP4和SbCASP-LP1C1，并进行了GUS染色及相对表达量测定等，确定了SbCASP4和SbCASP-LP1C1可以加强凯氏带聚合，增加质外体屏障的厚度，进而提高了过表达拟南芥的抗盐性。后续将继续探究SbCASP4和SbCASP-LP1C1基因在拒盐中的功能，为下一步利用转基因技术培育耐盐高产甜高粱新品种奠定基础。