Proline improves switchgrass growth and development by reduced lignin biosynthesis

Cong Guan,Hui-Fang Cen,Dan-Yang Tian,Yun-Wei Zhang,Dimiru Tadesse,Xin Cui

doi:10.1038/s41598-019-56575-9

Abstract

Transgenic switchgrass overexpressing Lolium perenne L. delta1-pyrroline 5-carboxylate synthase (LpP5CS) in group I (TG4 and TG6 line) and group II (TG1 and TG2 line) had significant P5CS and ProDH enzyme activities, with group I plants (TG4 and TG6) having higher P5CS and lower ProDH enzyme activity, while group II plants had higher ProDH and lower P5CS enzyme activity. We found group II transgenic plants showed stunted growth, and the changed proline content in overexpressing transgenic plants may influence the growth and development in switchgrass. RNA-seq analysis showed that KEGG enrichment included phenylpropanoid biosynthesis pathway among group I, group II and WT plants, and the expression levels of genes related to lignin biosynthesis were significantly up-regulated in group II. We also found that lignin content in group II transgenic plants was higher than that in group I and WT plants, suggesting that increased lignin content may suppress switchgrass growth and development. This study uncover that proline can appropriately reduce lignin biosynthesis to improve switchgrass growth and development. Therefore, appropriate reduction in lignin content and increase in biomass are important for bioenergy crop to lower processing costs for biomass fermentation-derived fuels.

Highlights

Switchgrass (Panicum virgatum L.) is a perennial C4 grass native to North America, considered as a potential dedicated bioenergy crop due to its high biomass production and tolerance on marginal land[9]
Combined with the proline levels, these results suggested that proline synthesis is reduced and proline degradation is enhanced in the group II plants compared with the WT plants, and while in group I, there is an increased proline synthesis and decreased proline degradation
pyrroline-5-carboxylate synthetase (P5CS) activity was lower in group II plants, which could led to the decreased proline accumulation

Summary

Introduction

Switchgrass (Panicum virgatum L.) is a perennial C4 grass native to North America, considered as a potential dedicated bioenergy crop due to its high biomass production and tolerance on marginal land[9]. We found that overexpression plants showed two different phenotypes, the two groups transgenic plants had different P5CS and ProDH enzyme activities, as well as proline content. To shed light on potential changes in growth and development, we analyzed the RNA-seq data. The results showed that phenylpropanoid biosynthesis pathway was significantly up-regulated in the group II plants compared with the group I and WT plants. Lignin content in group II transgenic plants was higher than that in group I and WT plants, suggesting that proline affects switchgrass growth and development by coordination with lignin biosynthesis

Methods

Results

Conclusion