Dhaliwal Lakhvir Kaur, Shim Junghyun, Auld Dick, Angeles-Shim Rosalyn B
Department of Plant and Soil Science, Davis College of Agricultural Sciences and Natural Resources, Texas Tech University, Lubbock, TX, United States.
Front Plant Sci. 2024 Feb 6;15:1286908. doi: 10.3389/fpls.2024.1286908. eCollection 2024.
The level of fatty acid unsaturation in seeds is one of the major determinants of cold germination ability, particularly in oilseeds. The presence of double bonds in unsaturated fatty acids creates bends that lowers their melting temperatures compared to saturated fatty acids. Unsaturated fatty acids with low melting points mobilize faster at low temperatures providing seeds with sufficient energy for germination.
To investigate the effects of fatty acid unsaturation on the ability of cotton seeds to germinate under cold conditions, four recombinant inbred lines (RILs) of cotton with unique fatty acid profiles were evaluated using a set of developmental and biochemical assays at 12°C (critically low temperature), 15°C (cardinal minimum temperature) and 30°C (optimum temperature). Furthermore, whole seed lipidome profiling using liquid chromatography with mass spectrometry was done to compare the lipid compositional changes at 12°C and 30°C after imbibing cotton seeds of all the six genotypes for 0 hours, 3 hours and 6 hours.
The RILs with higher unsaturation/saturation ratios registered robust germination performance, lower solute leakage, and optimum water uptake rates under cold stress. Imbibition at 30°C for 8 hours before cold exposure significantly improved the germination of cold sensitive genotypes, indicating that the first few hours of water uptake are critical for cold stress. Whole seed lipidome profiling of all the genotypes specifically associated cold germination ability with higher unsaturation levels of phospholipids during early imbibition. The presence of double bonds in phospholipids creates kinks that maintain the fluidity of cell membranes under low temperature. Membrane flexibility under cold conditions is essential for facilitating key germination events including membrane organization and respiration. The current results highlight the importance of fatty acid composition in cold germination ability of upland cotton.
种子中脂肪酸的不饱和程度是冷发芽能力的主要决定因素之一，在油籽中尤为如此。与饱和脂肪酸相比，不饱和脂肪酸中的双键会产生弯曲，从而降低其熔点。熔点低的不饱和脂肪酸在低温下能更快地动员起来，为种子发芽提供足够的能量。
为了研究脂肪酸不饱和度对棉花种子在低温条件下萌发能力的影响，使用一组发育和生化分析方法，在12°C（临界低温）、15°C（最低基本温度）和30°C（最适温度）下，对四个具有独特脂肪酸谱的棉花重组自交系（RILs）进行了评估。此外，采用液相色谱-质谱联用技术对全种子脂质组进行分析，以比较所有六种基因型的棉花种子在吸水0小时、3小时和6小时后，12°C和30°C下的脂质组成变化。
不饱和/饱和比更高的RILs在冷胁迫下表现出强劲的发芽性能、较低的溶质渗漏率和最佳的吸水率。在冷处理前于30°C吸水8小时可显著提高冷敏感基因型的发芽率，这表明最初几个小时的吸水对冷胁迫至关重要。对所有基因型的全种子脂质组分析表明，在早期吸水过程中，冷发芽能力与磷脂的较高不饱和水平密切相关。磷脂中的双键会产生扭结，从而在低温下维持细胞膜的流动性。低温条件下的膜柔韧性对于促进包括膜组织和呼吸作用在内的关键发芽事件至关重要。目前的结果突出了脂肪酸组成在陆地棉冷发芽能力中的重要性。
