陕北地区糜子根系对干旱胁迫的分子响应机理

Proso millet (Panicum miliaceum L.) is the important strategic reserves of coarse cereals resources and one of the first crop of agricultural planting structure adjustment, especially has obvious production advantage in northern shaanxi province. Roots is the most sensitive to drought of all organs, its growth and physiological metabolism directly affects growth, yield and quality in proso millet. Drought stress is the main limiting factors of high quality and yield, but the mechanism study of proso millet roots in response to drought stress is very weak. On the basis of former research that proso millet root morphology has significant sense under drought, with the two widely cultivated varieties (Yumi 2 and Yumi 3) as the research object, root morphology, anatomical structure and key physiological indicators will be systematically studied by using combined indoor simulation with field in-situ experiment, which is aim to find out the most sensitive period of root response to drought. Proso millet roots transcriptomic changes was analyzed by using the RNA-Seq technology. The GO and KEGG pathway enrichment analysis were conducted for identifying related drought-resistant signaling pathways and key drought resistance genes of proso millet roots. Subsequently, the differential expressed genes certified by qRT-PCR. Genes considered involving proso millet drought resistance were chosen and the expression in different varieties with different level resistance and different drought treatments by qRT-PCR. The obtained results will be beneficial to reveal proso millet drought resistance molecular mechanism, and provide theory basis for breeding proso millet drought tolerant variety.

糜子是我国干旱半干旱地区重要的战略贮备性杂粮资源，是农业种植业结构调整的首选作物之一，尤其在陕北地区具有明显的生产优势。糜子根系是感知干旱胁迫最敏感的器官，其生长及生理代谢直接影响糜子生长发育及产量与品质。干旱胁迫是制约糜子优质高产的主要限制因子，但糜子根系响应干旱胁迫的机理研究十分薄弱。项目在前期研究发现糜子根系形态受干旱胁迫具有明显感知的基础上，以榆糜2号和3号等主栽品种为材料，通过室内模拟和田间原位试验，系统研究糜子不同生育期在干旱胁迫下根系形态指标、解剖结构和关键生理指标的变化，找出根系响应差异最敏感的时期；利用RNA-Seq技术分析不同处理下糜子根系转录组变化，筛选糜子根系应答干旱胁迫的差异表达基因，结合生物信息学分析方法鉴定糜子根系抗旱的相关信号通路及关键抗旱基因；通过定量PCR技术验证关键抗旱基因在糜子根系中的表达，揭示糜子抗旱分子机理，为糜子耐旱品种选育提供理论依据。

干旱胁迫是制约糜子优质高产的主要限制因子，根系是感知干旱胁迫最敏感的器官，但目前关于糜子根系响应干旱胁迫的机理尚不清楚。本研究以陕北地区主栽糜子品种榆糜3号（耐旱性强）和榆糜2号（旱敏感）为研究对象，采用室内模拟试验和田间原位试验相结合的方法，从形态指标、解剖结构、关键生理指标及转录组数据等方面，系统研究糜子根系对干旱胁迫的分子响应机理。结果表明：（1）不同时期干旱胁迫对糜子根系各形态指标影响程度不同。干旱条件下，两个糜子品种根系皮层细胞面积、皮层厚度、中柱面积、导管面积和直径均呈现下降趋势；四个生育时期中，灌浆期不同程度干旱胁迫对糜子单株产量影响最大，并且榆糜3号根系形态和根系显微结构受干旱胁迫影响程度低于榆糜2号。（2）灌浆期不同程度干旱胁迫下，与榆糜2号相比，干旱胁迫下榆糜3号根系可溶性蛋白含量降低幅度较小，SOD活性、POD活性增加幅度较大，而MDA含量增加幅度较小。干旱胁迫会促进两个品种根系产生IAA、ABA和GA3，而对两个品种根系JA含量具有抑制作用；干旱胁迫对两个糜子品种根系SA含量影响效果不同。（3）干旱胁迫后榆糜2号和榆糜3号根系中共同的DEGs为6847个。GO富集分析显示，榆糜3号上调主要富集在植物甾体代谢过程、纤维素生物合成过程、油菜素内酯代谢过程等生物学过程。KEGG富集分析显示，干旱胁迫下甾体生物合成、油菜素内酯的生物合成、生物素代谢、糖胺聚糖降解等相关基因在两糜子品种中均显著富集，并且在榆糜3号中的表达明显高于榆糜2号，这些基因的差异表达导致了两个品种的抗旱性差异，且苯丙烷代谢在提高两个糜子品种耐旱性中均起到了积极作用。GO富集分析与KEGG富集分析显示，榆糜2号经干旱胁迫后下调的DEGs在MAPK信号通路、钙离子结合代谢通路中显著富集，而榆糜3号无显著富集，这也可能是榆糜2号抗旱性低于榆糜3号的原因之一。本研究结果可为揭示糜子抗旱分子机理提供科学依据。