Abstract
Main conclusionA 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.
Highlights
The rhizosphere microbiome composition promotes plant growth by nutrient solubilization, carbon sequestration, nitrogen fixation, induction of disease resistance, and phytohormone biosynthesis in plants (Mabood et al 2014; Smith et al 2015)
Microbiome of plants acts as secondary genome as plants interact with a plethora of microbes in their lifecycle that colonize or inhabit in different compartments of roots such as rhizosphere, rhizoplane, endosphere, and phyllosphere which affects the plant growth, productivity, carbon sequestration and phytoremediation (Bulgarelli et al 2012; Lundberg et al 2012; Turner et al 2013)
The rhizosphere microbiome is greatly influenced by the nature of the root exudates, mucilage and sloughed cells (Moe 2013)
Summary
The rhizosphere microbiome composition promotes plant growth by nutrient solubilization, carbon sequestration, nitrogen fixation, induction of disease resistance, and phytohormone biosynthesis in plants (Mabood et al 2014; Smith et al 2015). Root exudate composition is very critical in selective enrichment of microbial species around the rhizosphere (Bais et al 2006) These exudates are rich in phenolic compounds, carbohydrates, proteins, among which flavonoids play a critical role in attracting beneficial microbes and in plant defenses against pathogens, herbivores and environmental stress (Treutter 2005). Plant roots use these biochemicals as molecular signals to attract, repel, or maintain microbial species in the rhizosphere (Tseng et al 2009; Nelson and Sadowsky 2015). Understanding the genetic and molecular mechanisms behind the root secretion system and root exudate composition is important for the fundamental understanding of plant-microbe interaction, as well as to design strategies for crop improvement
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
