Regulation of small RNAs and corresponding targets in Nod factors-induced Phaseolus vulgaris root hair cells

A Phaseolus vulgaris genome-wide analysis led to identify the small RNAs (sRNA) of this agronomical important legume. It revealed newly identified P. vulgaris-specific microRNAs (miRNAs) that could be involved in the regulation of the rhizobia-symbiotic process. Generally, novel miRNAs are difficult to identify and study because they are very lowly expressed in a tissue- or cell-specific manner. We aimed to analyze sRNAs from common bean root hairs (RH), a single-cell model, induced with pure Rhizobium etli-Nod factors (NF), a unique type of signal molecule. The sequence analysis of samples from NF-induced and control libraries led to identify 132 mature miRNAs, including 63 novel miRNAs and 1984 phasiRNAs. From these, six miRNAs were significantly differentially expressed during NF-induction, including one novel miRNA: miR-RH82. A parallel degradome analysis of the same samples revealed 29 targets potentially cleaved by novel miRNAs specifically in NF-induced RH samples, however these novel miRNAs were not differentially accumulated in this tissue. This study reveals Phaseolus vulgaris-specific novel miRNA candidates and their corresponding targets that meet all criteria to be involved in the regulation of the early nodulation events. Overall design: Small RNA sequencing from Nod factor-induced Phaseolus vulgaris root hairs