Abstract
Gamma-aminobutyric acid (GABA) may play a positive role in regulating plant tolerance to drought or heat stress. The objectives of this study were to investigate the physiological effects of GABA on tolerance of creeping bentgrass (Agrostis stolonifera) to heat and drought stress and to determine whether enhanced heat and drought tolerance due to GABA treatment was associated with the up-regulation of selected genes and transcriptional factors involved in stress protection. Creeping bentgrass (cultivar “Penncross”) plants were treated with 0.5 mM GABA or water (untreated control) as a foliar spray and were subsequently exposed to heat stress (35/30 °C, day/night), drought stress by withholding irrigation, or non-stress conditions in controlled-environment growth chambers. Exogenous application of GABA significantly improved plant tolerance to heat and drought stress, as reflected by increased leaf water content, cell membrane stability, and chlorophyll content. The analysis of gene transcript level revealed that exogenous GABA up-regulated the expression of ABF3, POD, APX, HSP90, DHN3, and MT1 during heat stress and the expression of CDPK26, MAPK1, ABF3, WRKY75, MYB13, HSP70, MT1, 14-3-3, and genes (SOD, CAT, POD, APX, MDHAR, DHAR, and GR) encoding antioxidant enzymes during drought stress. The up-regulation of the aforementioned stress-protective genes and transcriptional factors could contribute to improved heat and drought tolerance in creeping bentgrass.
Highlights
Abiotic stresses such as heat and drought stress limit plant growth in many areas of the world [1,2]
The photochemical efficiency (Fv/Fm) ratio increased by 8% and 10% in Gamma-aminobutyric acid (GABA)-treated plants compared to non-treated plants under heat and drought stress, respectively (Figure 2B)
Our results demonstrated that exogenous application of GABA could significantly improve heat and drought tolerance in creeping bentgrass, as reflected by less leaf water deficit and oxidative damage, higher cell membrane stability, and higher chlorophyll content under prolonged heat and drought stress
Summary
Abiotic stresses such as heat and drought stress limit plant growth in many areas of the world [1,2]. Plants have developed multiple adaptive mechanisms such as the activation of stress-protective genes encoding heat shock proteins (HSPs), dehydrins (DHNs), metallothionein (MT), and proteins involved in antioxidant metabolism, as well as many transcriptional factors, such as the WRKY, MYB, and bZIP family [6,7,8,9,10] Approaches such as exogenous application of plant growth regulators (PGR) that can induce or enhance the expression of stress-protective genes and transcriptional factors are found to be effective in improving tolerance to heat and drought stress in perennial grass and other plant species [9,11,12]. Limited information is available regarding common or specific genes’ expression regulated by GABA that may be associated with improved heat and drought tolerance when plants are subjected to these stresses
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