Abstract
Perennial ryegrass (Lolium perenne L.) is an important cool-season grass species that is widely cultivated in temperate regions worldwide but usually sensitive to heat stress. Jasmonates (JAs) may have a positive effect on plant tolerance under heat stress. In this study, results showed that exogenous methyl jasmonic acid (MeJA) could significantly improve heat tolerance of perennial ryegrass through alteration of osmotic adjustment, antioxidant defense, and the expression of JA-responsive genes. MeJA-induced heat tolerance was involved in the maintenance of better relative water content (RWC), the decline of chlorophyll (Chl) loss for photosynthetic maintenance, as well as maintained lower electrolyte leakage (EL) and malondialdehyde (MDA) content under heat condition, so as to avoid further damage to plants. Besides, results also indicated that exogenous MeJA treatment could increase the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), thus enhancing the scavenging ability of reactive oxygen species, alleviating the oxidative damage caused by heat stress. Heat stress and exogenous MeJA upregulated transcript levels of related genes (LpLOX2, LpAOC, LpOPR3, and LpJMT) in JA biosynthetic pathway, which also could enhance the accumulation of JA and MeJA content. Furthermore, some NAC transcription factors and heat shock proteins may play a positive role in enhancing resistance of perennial ryegrass with heat stress.
Highlights
Perennial ryegrass (Lolium perenne L.) is native to Asia, Europe, and northern Africa and becomes a crucial grass species widely cultivated in temperate regions as high-quality forage and turfgrass (Yu et al, 2015)
Leaves turned yellow and wilting after 14 days of heat stress in H and H + methyl jasmonic acid (MeJA) group, but MeJA-pretreated plants in the H + MeJA group were greener than untreated plants
Previous studies have found that exogenous MeJA could increase Chl content and improve the tolerance of cowpea (Vigna sinensis) and Brassica napus (Ahmadi et al, 2018) under salinity stress (Sadeghipour, 2017)
Summary
Perennial ryegrass (Lolium perenne L.) is native to Asia, Europe, and northern Africa and becomes a crucial grass species widely cultivated in temperate regions as high-quality forage and turfgrass (Yu et al, 2015). It has many desirable agronomic qualities, such as long growing season with strong adaptability, rapid establishment as a primary turf species, and high forage yield under suitable. The amount of MeJA increases significantly, which promotes the biosynthesis of some substances related to environmental stress (such as hormone and proline) and induces the expression of a series of genes related to stress tolerance, enhancing the plant resistance (Wasternack, 2014). Trauma and other stress factors that induce the JA response could promote the expression of these genes, and the activation of these gene transcription occurs at the site of JA synthesis (Dhondt et al, 2000; Halitschke and Baldwin, 2003; Stenzel et al, 2003; Matsul, 2006; Tomoyuki et al, 2008)
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