MicroRNA Expression Analysis in the Cellulosic Biofuel Crop Switchgrass (Panicum virgatum) under Abiotic Stress

Guiling Sun,Baohong Zhang,Peng Xiao,C Neal Stewart

doi:10.1371/journal.pone.0032017

Abstract

Switchgrass has increasingly been recognized as a dedicated biofuel crop for its broad adaptation to marginal lands and high biomass. However, little is known about the basic biology and the regulatory mechanisms of gene expression in switchgrass, particularly under stress conditions. In this study, we investigated the effect of salt and drought stress on switchgrass germination, growth and the expression of small regulatory RNAs. The results indicate that salt stress had a gradual but significant negative effect on switchgrass growth and development. The germination rate was significantly decreased from 82% for control to 36% under 1% NaCl treatment. However, drought stress had little effect on the germination rate but had a significant effect on the growth of switchgrass under the severest salinity stress. Both salt and drought stresses altered the expression pattern of miRNAs in a dose-dependent manner. However, each miRNA responded to drought stress in a different pattern. Salt and drought stress changed the expression level of miRNAs mainly from 0.9-fold up-regulation to 0.7-fold down-regulation. miRNAs were less sensitive to drought treatment than salinity treatment, as evidenced by the narrow fold change in expression levels. Although the range of change in expression level of miRNAs was similar under salt and drought stress, no miRNAs displayed significant change in expression level under all tested salt conditions. Two miRNAs, miR156 and miR162, showed significantly change in expression level under high drought stress. This suggests that miR156 and miR162 may attribute to the adaption of switchgrass to drought stress and are good candidates for improving switchgrass as a biofuel crop by transgenic technology.

Highlights

Switchgrass (Panicum virgatum L.) is a warm-season perennial grass that is native to North America
Despite of its increasing importance as a biofuel crop, we still know very little about the basic biology of switchgrass under abiotic stress conditions, such as those posed by salt and drought; important characteristics to characterize include seed germination, plant growth, and the regulation mechanism of gene expression when plants are under stress
The effect of salt and drought stresses on switchgrass growth and development We studied several response variables in salt and drought stress treatments: switchgrass germination rate, biomass accumulation, development of leaves and roots, and gene expression dynamics of multiple miRNA genes

Summary

Introduction

Switchgrass (Panicum virgatum L.) is a warm-season perennial grass that is native to North America. Despite of its increasing importance as a biofuel crop, we still know very little about the basic biology of switchgrass under abiotic stress conditions, such as those posed by salt and drought; important characteristics to characterize include seed germination, plant growth, and the regulation mechanism of gene expression when plants are under stress. Such baseline data are needed to gauge the effects of genetic improvements and to guide researchers to appropriate gene candidates to manipulate for improving stress tolerance. Important abiotic stresses in this regard include salinity [12], drought [13,14], cold [15], and heavy metals [16], nutrition, and other stresses [11]

Methods

Results

Conclusion