Abstract
Understanding the changes in peanut (Arachis hypogaea L.) anther lipidome under heat stress (HT) will aid in understanding the mechanisms of heat tolerance. We profiled the anther lipidome of seven genotypes exposed to ambient temperature (AT) or HT during flowering. Under AT and HT, the lipidome was dominated by phosphatidylcholine (PC), phosphatidylethanolamine (PE), and triacylglycerol (TAG) species (> 50% of total lipids). Of 89 lipid analytes specified by total acyl carbons:total carbon–carbon double bonds, 36:6, 36:5, and 34:3 PC and 34:3 PE (all contain 18:3 fatty acid and decreased under HT) were the most important lipids that differentiated HT from AT. Heat stress caused decreases in unsaturation indices of membrane lipids, primarily due to decreases in highly-unsaturated lipid species that contained 18:3 fatty acids. In parallel, the expression of Fatty Acid Desaturase 3-2 (FAD3-2; converts 18:2 fatty acids to 18:3) decreased under HT for the heat-tolerant genotype SPT 06-07 but not for the susceptible genotype Bailey. Our results suggested that decreasing lipid unsaturation levels by lowering 18:3 fatty-acid amount through reducing FAD3 expression is likely an acclimation mechanism to heat stress in peanut. Thus, genotypes that are more efficient in doing so will be relatively more tolerant to HT.
Highlights
Understanding the changes in peanut (Arachis hypogaea L.) anther lipidome under heat stress (HT) will aid in understanding the mechanisms of heat tolerance
We found that wheat pollen lipid composition is significantly altered by high temperatures, and some lipids are highly heat-responsive, in particular, the extraplastid-localized phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE)[15]
We evaluated a total of seven peanut genotypes in two growing seasons (2018 and 2019) at high temperature (HT, heat stress; 41/27 °C for 2018 and 38/26 °C for 2019, average day/night temperatures imposed for 17 days and 18 days during flowering in 2018 and 2019, respectively) and ambient temperature (AT, control; 31/22 °C for 2018 and 28/22 °C for 2019) under field conditions
Summary
Understanding the changes in peanut (Arachis hypogaea L.) anther lipidome under heat stress (HT) will aid in understanding the mechanisms of heat tolerance. Our results suggested that decreasing lipid unsaturation levels by lowering 18:3 fatty-acid amount through reducing FAD3 expression is likely an acclimation mechanism to heat stress in peanut. It has been reported that a daytime temperature of 38 °C caused the greatest yield reduction when stress occurred from 6 days before to 15 days after flowering[7] This reduction was primarily due to fewer flowers producing pegs (a peg is a stalk-like structure formed at the base of the ovary, which enters the soil and forms a pod at the tip). Wheat plants decreased pollen lipid unsaturation levels to adapt to heat stress and underwent lipid remodeling, likely to prevent the phase transition of membranes from a bilayer to a non-bilayer phase. DS25-1 had significant decreases in the expression levels of the fatty-acid desaturase (FAD) genes FAD3A and FAD3B, which convert linoleic (18:2) acid to linolenic (18:3) acid
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