Differential Responses of Polyamines and Antioxidants to Drought in a Centipedegrass Mutant in Comparison to Its Wild Type Plants.

Mingxi Liu,Zhenfei Guo,Shaoyun Lu,Jingjing Chen

doi:10.3389/fpls.2017.00792

Abstract

Centipedegrass (Eremochloa ophiuroides [Munro] Hack.) is an important warm-season turfgrass species with low turf maintenance requirements. However, our knowledge on physiological adaptation of centipedegrass to drought stress is limited. Physiological responses to drought in a gamma-ray-induced mutant 22-1 as compared with two wild type (WT) lines were analyzed for understanding of drought tolerance mechanism of centipedegrass. The mutant showed an elevated drought tolerance with higher levels of relative water content, net photosynthetic rate (A) and stomatal conductance (gs) and lower levels of ion leakage and malondialdehyde (MDA) under drought stress as compared with WT plants. A showed significant correlation with gs and MDA. Higher levels of antioxidant enzymes activities, non-enzyme antioxidants, and polyamines including putrescine (Put), spermidine (Spd), and spermine (Spm) were maintained in 22-1 than in WT plants. Superoxide dismutase (SOD), catalase (CAT), ascorbate-peroxidase (APX), and glutathione reductase (GR) activities and ascorbic acid (AsA) content were significantly correlated with both Put and Spd levels, and reduced glutathione level was correlated with Put during drought stress. Exogenous application of Put, Spd, and Spm increased drought tolerance and activities of SOD, CAT, APX, and GR in WT plants. The results suggest that higher levels of polyamines and antioxidant defense system are associated with the elevated drought tolerance in 22-1, which may improve protection on photosynthesis against drought induced oxidative damage.

Highlights

Plant adaptation to drought involves various physiological responses
The results showed that higher levels of polyamines and antioxidant defense system were maintained in 22-1 than in wild type (WT) plants under drought stress conditions, while the higher activities of antioxidant enzymes were associated with polyamine levels
The Mutant 22-1 had Elevated Drought Tolerance Compared with Its WT Plants

Summary

Introduction

Plant adaptation to drought involves various physiological responses. A desiccation-induced closure of stomata limits CO2 availability and reduces fixation through Bensen cycle and utilization of photo-generated reductant under drought, which leads to elevated production of reactive oxygen species (ROS), including superoxide radicals, hydrogen peroxide (H2O2) and hydroxyl radicals, by the water–water cycle (Asada, 1999). Polyamines accumulate in rice (Oryza sativa L.) in response to drought and are associated with drought tolerance (Capell et al, 2004; Yang et al, 2007). Overexpression of arginine decarboxylase (ADC) and S-adenosylmethionine decarboxylase (SAMDC), the key genes for polyamine synthesis, resulted in elevated levels of Put, Spd, and Spm and enhanced drought tolerance in transgenic rice and tobacco plants (Waie and Rajam, 2003; Capell et al, 2004; Wi et al, 2014), while down-regulation of SAMDC gene decreased Spd and Spm levels and polyamines and led to reduced drought tolerance in transgenic rice plants (Chen et al, 2014)

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