Fiber and Biopolymer Research Institute (FBRI), Department of Plant and Soil Science, Texas Tech University, Lubbock, TX, 79409, USA.
Department of Plant and Soil Science, Texas Tech University, Lubbock, 79409, USA.
Planta. 2021 Jan 18;253(2):33. doi: 10.1007/s00425-021-03569-5.
A novel inducible secretion system mutation in Sorghum named Red root has been identified. The mutant plant root exudes pigmented compounds that enriches Actinobacteria in its rhizosphere compared to BTx623. Favorable plant-microbe interactions in the rhizosphere positively influence plant growth and stress tolerance. Sorghum bicolor, a staple biomass and food crop, has been shown to selectively recruit Gram-positive bacteria (Actinobacteria) in its rhizosphere under drought conditions to enhance stress tolerance. However, the genetic/biochemical mechanism underlying the selective enrichment of specific microbial phyla in the sorghum rhizosphere is poorly known due to the lack of available mutants with altered root secretion systems. Using a subset of sorghum ethyl methanesulfonate (EMS) mutant lines, we have isolated a novel Red root (RR) mutant with an increased accumulation and secretion of phenolic compounds in roots. Genetic analysis showed that RR is a single dominant mutation. We further investigated the effect of root-specific phenolic compounds on rhizosphere microbiome composition under well-watered and water-deficit conditions. The microbiome diversity analysis of the RR rhizosphere showed that Actinobacteria were enriched significantly under the well-watered condition but showed no significant change under the water-deficit condition. BTx623 rhizosphere showed a significant increase in Actinobacteria under the water-deficit condition. Overall, the rhizosphere of RR genotype retained a higher bacterial diversity and richness relative to the rhizosphere of BTx623, especially under water-deficit condition. Therefore, the RR mutant provides an excellent genetic resource for rhizosphere-microbiome interaction studies as well as to develop drought-tolerant lines. Identification of the RR gene and the molecular mechanism through which the mutant selectively enriches microbial populations in the rhizosphere will be useful in designing strategies for improving sorghum productivity and stress tolerance.
已鉴定出高粱中一种名为红根的新型诱导分泌系统突变体。与 BTx623 相比，突变体植物根部渗出的有色化合物使根际放线菌富集。根际中有利的植物-微生物相互作用正向影响植物生长和胁迫耐受性。高粱，一种主要的生物质和粮食作物，已被证明在干旱条件下选择性地在其根际招募革兰氏阳性细菌（放线菌），以增强胁迫耐受性。然而，由于缺乏改变根分泌系统的可用突变体，高粱根际中特定微生物类群选择性富集的遗传/生化机制知之甚少。使用高粱乙基甲磺酸（EMS）突变体系的一个子集，我们分离到一个新的红根（RR）突变体，该突变体在根中积累和分泌酚类化合物增加。遗传分析表明，RR 是一个单一的显性突变。我们进一步研究了根特异性酚类化合物对根际微生物组组成的影响，在充分浇水和缺水条件下。RR 根际的微生物组多样性分析表明，在充分浇水条件下放线菌显著富集，但在缺水条件下没有显著变化。BTx623 根际在缺水条件下放线菌显著增加。总体而言，RR 基因型的根际保留了比 BTx623 根际更高的细菌多样性和丰富度，尤其是在缺水条件下。因此，RR 突变体为根际-微生物相互作用研究以及开发耐旱系提供了极好的遗传资源。鉴定 RR 基因以及突变体选择性富集根际微生物种群的分子机制，将有助于设计提高高粱生产力和胁迫耐受性的策略。
