An ABC Transporter Mutation Alters Root Exudation of Phytochemicals That Provoke an Overhaul of Natural Soil Microbiota      

Abstract

Root exudates influence the surrounding soil microbial community, and recent evidence demonstrates the involvement of ATPbinding cassette (ABC) transporters in root secretion of phytochemicals. In this study, we examined effects of seven Arabidopsis (Arabidopsis thaliana) ABC transporter mutants on the microbial community in native soils. After two generations, only the Arabidopsis abcg30 (Atpdr2) mutant had significantly altered both the fungal and bacterial communities compared with the wild type using automated ribosomal intergenic spacer analysis. Similarly, root exudate profiles differed between the mutants; however, the largest variance from the wild type (Columbia-0) was observed in abcg30, which showed increased phenolics and decreased sugars. In support of this biochemical observation, whole-genome expression analyses of abcg30 roots revealed that some genes involved in biosynthesis and transport of secondary metabolites were up-regulated, while some sugar transporters were down-regulated compared with genome expression in wild-type roots. Microbial taxa associated with Columbia-0 and abcg30 cultured soils determined by pyrosequencing revealed that exudates from abcg30 cultivated a microbial community with a relatively greater abundance of potentially beneficial bacteria (i.e. plant-growth-promoting rhizobacteria and nitrogen fixers) and were specifically enriched in bacteria involved in heavy metal remediation. In summary, we report how a single gene mutation from a functional plant mutant influences the surrounding community of soil organisms, showing that genes are not only important for intrinsic plant physiology but also for the interactions with the surrounding community of organisms as well.

Spatio Temporal Influence of Isoflavonoids on Bacterial Diversity in the Soybean Rhizosphere

“…In the latter case, the availability of genetic mutants impaired in biosynthesis and transport of specific rhizodeposit compounds has been crucial. For example, mutations in an Arabidopsis thaliana ABC-transporter gene, ABCG30 (resulting in increased exudation of phenolic acids and reduced exudation of sugars), caused significant changes in root microbial community structure as assayed by high-throughput sequencing of rRNA gene amplicons (Badri et al 2008(Badri et al , 2009). This study revealed the association of a number of potentially beneficial bacteria with abcg30 mutant roots.…”

A petunia ABC protein controls strigolactone-dependent symbiotic signalling and branching

“…The rationale behind the focus on these transporters, of which there are 15 in Arabidopsis 11 , 23 in Oryza sativa (rice) 11 and 23 putative factors in Solanum lycopersicum (tomato) ( Supplementary Fig. 3a), was that they are plasma membrane proteins often found in roots 12 , they are implicated in below-ground plantmicrobe interactions 13,14 , and they have affinities for compounds that are structurally related to strigolactones 8,9,15 . Of six primary candidates, only P. hybrida PDR1 had increased expression in roots that were subjected to either phosphate starvation (Fig.…”

Flavonoids in plant rhizospheres: secretion, fate and their effects on biological communication

“…For example, at least 54 flavonoid compounds have been identified in Arabidopsis (Saito et al 2013), with flavanone detected among the secreted phenolic compounds, such as coumarin, syringic acid and vanillic acid, in root exudates (Toussaint et al 2012). An analysis of the effects of various mutations in ABC transporter genes of Arabidopsis on the composition of root exudates and soil microbial communities showed that root exudates from the abcg30/pdr2 mutant contained more phenolic compounds and fewer sugars than the exudates of wild type plants (Badri et al 2009). Because this mutation altered the expression of many genes, the differences in root exudate composition may not have been due to the direct effects of mutation in this ABC transporter gene but to the pleiotropic effects of the gene mutation.…”