Overexpression of PvWOX3a in switchgrass promotes stem development and increases plant height

Ruijuan Yang,Zhichao Sun,Shaojun Dai,Yuzhu Huo,Mengqi Wang,Wenwen Liu,Zhenying Wu,Chen Bai,Hailing Zhang,Yamei Wang,Huapeng Zhou,Chunxiang Fu

doi:10.1038/s41438-021-00678-w

Abstract

Switchgrass (Panicum virgatum L.) is an important perennial, noninvasive, tall ornamental grass that adds color and texture to gardens and landscapes. Moreover, switchgrass has been considered a forage and bioenergy crop because of its vigorous growth, low-input requirements, and broad geography. Here, we identified PvWOX3a from switchgrass, which encodes a WUSCHEL-related homeobox transcription factor. Transgenic overexpression of PvWOX3a in switchgrass increased stem length, internode diameter, and leaf blade length and width, all of which contributed to a 95% average increase in dry weight biomass compared with control plants. Yeast one-hybrid and transient dual-luciferase assays showed that PvWOX3a can repress the expression of gibberellin 2-oxidase and cytokinin oxidase/dehydrogenase through apparently direct interaction with their promoter sequences. These results suggested that overexpression of PvWOX3a could increase gibberellin and cytokinin levels in transgenic switchgrass plants, which promotes cell division, elongation, and vascular bundle development. We also overexpressed PvWOX3a in a transgenic miR156-overexpressing switchgrass line that characteristically exhibited more tillers, thinner internodes, and narrower leaf blades. Double transgenic switchgrass plants displayed significant increases in internode length and diameter, leaf blade width, and plant height but retained a tiller number comparable to that of plants expressing miR156 alone. Ultimately, the double transgenic switchgrass plants produced 174% more dry-weight biomass and 162% more solubilized sugars on average than control plants. These findings indicated that PvWOX3a is a viable potential genetic target for engineering improved shoot architecture and biomass yield of horticulture, fodder, and biofuel crops.

Highlights

In vascular plants, the shoot system usually grows aboveground; it determines the morphology of the plant and comprises the aerial biomass
GA12 is converted into bioactive GA1, which is regulated by three dioxygenases, GA 20-oxidase (GA20ox), GA 3-oxidase (GA3ox), and GA 2-oxidase (GA2ox)[11]
Phylogenetic analysis showed that the PvWOXs were clustered into three distinct clades, namely, an ancient clade, an intermediate clade, and a modern WUS clade, which aligned with previously published phylogenies[41] (Fig. 1a)

Summary

Introduction

The shoot system usually grows aboveground; it determines the morphology of the plant and comprises the aerial biomass. Each phytomer is made up of an internode, Yang et al Horticulture Research (2021)8:252 affects other aspects of plant development and growth and serves as a major contributing factor in determining plant morphology and aboveground biomass. GA12 is converted into bioactive GA1, which is regulated by three dioxygenases, GA 20-oxidase (GA20ox), GA 3-oxidase (GA3ox), and GA 2-oxidase (GA2ox)[11]. Among these enzymes, GA2ox irreversibly catalyzes the conversion of bioactive GA or its precursors via 2-β hydroxylation into inactive catabolites[11].

Methods

Results

Conclusion