Gibberellin-Regulation and Genetic Variations in Leaf Elongation for Tall Fescue in Association with Differential Gene Expression Controlling Cell Expansion.

Qian Xu,Qian Xu,Sanalkumar Krishnan,Emily Merewitz,Jichen Xu,Bingru Huang,Bingru Huang,Bingru Huang

doi:10.1038/srep30258

Abstract

Leaf elongation rate (LER) is an important factor controlling plant growth and productivity. The objective of this study was to determine whether genetic variation in LER for a fast-growing (‘K-31’), and a dwarf cultivar (‘Bonsai’) of tall fescue (Festuca arundinacea) and gibberellic acid (GA) regulation of LER were associated with differential expression of cell-expansion genes. Plants were treated with GA3, trinexapac-ethyl (TE) (GA inhibitor), or water (untreated control) in a hydroponic system. LER of ‘K-31’ was 63% greater than that of ‘Bonsai’, which corresponded with 32% higher endogenous GA4 content in leaf and greater cell elongation and production rates under the untreated control condition. Exogenous application of GA3 significantly enhanced LER while TE treatment inhibited leaf elongation due to GA3-stimulation or TE-inhibition of cell elongation and production rate in leaves for both cultivars. Real-time quantitative polymerase chain reaction analysis revealed that three α-expansins, one β-expansin, and three xyloglucan endotransglycosylase (XET) genes were associated with GA-stimulation of leaf elongation, of which, the differential expression of EXPA4 and EXPA7 was related to the genotypic variation in LER of two cultivars. Those differentially-expressed expansin and XET genes could play major roles in genetic variation and GA-regulated leaf elongation in tall fescue.

Highlights

Low-Leaf elongation rate (LER) cultivar (18 mm d−1), suggesting genotypic variation in LER related to both cell elongation and production rate[14]
Cell elongation is controlled by cell extensibility, which is regulated by cell-wall loosening proteins and enzymes including expansin and xyloglucan endotransglycosylase (XET)[15,16]
It is hypothesized that the genetic variation in leaf elongation between fast-growing and dwarf-type tall fescue cultivars could be regulated by differential responses to gibberellic acid (GA), endogenous production of GA, and/or differential expression of cell-wall loosening genes controlling cell elongation

Summary

Introduction

Low-LER cultivar (18 mm d−1), suggesting genotypic variation in LER related to both cell elongation and production rate[14]. Tall fescue has wide genetic variation in leaf elongation rate, with cultivars of fast-growing or slow-growing (or dwarf-type) phenotypes widely used as forage and turf grasses, respectively[41,42]. It is hypothesized that the genetic variation in leaf elongation between fast-growing and dwarf-type tall fescue cultivars could be regulated by differential responses to GA, endogenous production of GA, and/or differential expression of cell-wall loosening genes controlling cell elongation. The objectives of this study were to determine GA-regulation of leaf elongation and differential expression of several expansin and XET genes associated with the genetic variations in leaf elongation rate by comparing a fast-growing cultivar ‘K-31’ and a dwarf-type cultivar ‘Bonsai’

Objectives

Methods

Results

Discussion

Conclusion