Laser Microdissection of Pisum sativum L. Nodules Followed by RNA-Seq Analysis Revealed Crucial Transcriptomic Changes during Infected Cell Differentiation

Garden pea (Pisum sativum L.) is a globally important legume crop. Like other legumes, it forms beneficial symbiotic interactions with the soil bacteria rhizobia, gaining the ability to fix atmospheric nitrogen. In pea nodules, the meristem is long-lasting and results in the formation of several histological zones that implicate a notable differentiation of infected host cells. However, the fine transcriptional changes that accompany differentiation are still unknown. In this study, using laser microdissection followed by RNA-seq analysis, we performed transcriptomic profiling in the early infection zone, late infection zone, and nitrogen fixation zone of 11-day-old nodules of pea wild-type line SGE. As a result, a list of functional groups of differentially expressed genes (DEGs) in different nodule histological zones and a list of genes with the most prominent expression changes during nodule development were obtained. Their analyses demonstrated that the highest amount of DEGs was associated with the nitrogen fixation zone. Among well-known genes controlling nodule development, we revealed genes that can be novel players throughout nodule formation. The characterized genes in pea were compared with those previously described in other legumes and their possible functions in nodule development are discussed.

Automated summary

In this study, transcriptomic profiling in different histological zones of pea nodules revealed that the nitrogen fixation zone had the highest amount of differentially expressed genes (DEGs). Some novel genes were identified as potential players in nodule formation, and comparisons with genes from other legumes were made to discuss their possible functions in nodule development.