Soybean Root Hair, a Single Cell Model to Study Plant-Microbe Interactions, Abiotic Stress and Epigenetic Regulation

It is well known that Biological N₂ fixation (BNF) has a significant role in the agricultural production of leguminous crops. In most legumes, the N₂ fixation process is mediated by rhizobial infection via root hairs, single cell extensions of the root epidermis. In order to study the early phases of the symbiotic interaction in detail, we developed a method to isolate soybean root hair cells in quantity and use this system as a plant model for single cell, systems biology.

Previous work focused on the analysis of the soybean root hair cell transcriptome, proteome, phosphoproteome, metabolome, and small RNA composition. These studies led to the identification of a variety of genes involved in the nodulation processes. Recently, we focused our attention on understanding the role of epigenetics in the control of nodulation events. We generated small RNA libraries from B. japonicum infected root hairs, un-infected root hairs and from stripped roots. Sequencing identified 114 miRNAs of which 61 miRNAs were regulated significantly after B. japonicum infection. Specific examples will be shown of the regulation of key nodulation genes by miRNAs, clearly indicating that this form of regulation is very important for the nodulation process.

Given the utility of the soybean root hair cell system, we have expanded its use to examine the impact of abiotic stress factors by means of transcriptomic and proteomic, as well as epigenetic (cytosine DNA methylation), approaches. We specifically examined the effect of heat and drought, stresses that might be associated with climate impacts due to global warming.