Evaluating role of phosphatidic acid in cold stress tolerance in silage-corn

Wu, Jiaxu (2022) Evaluating role of phosphatidic acid in cold stress tolerance in silage-corn. Masters thesis, Memorial University of Newfoundland.

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Abstract

Extreme cold weather conditions and short growing seasons during early seedling establishment are the major causes of the low forage yield of silage corn (Zea mays L.). The experiments were conducted under controlled environmental conditions to determine the effects of different temperature regimes (25°C, 20°C, 15°C, 10°C and 5°C) on morphological, physiological and biochemical attributes of two silage-corn genotypes (Yukon-R, A4177G3-RIB) during the early growth stage. Results indicated that cold stress significantly affected seedling growth, photosynthesis, reactive oxygen species (ROS) accumulation and antioxidant enzyme activities. The chlorophyll content, photosynthetic rate, and maximal photochemical efficiency of photosystem-II were drastically decreased under cold conditions. Besides, cold stress induced the accumulation of hydrogen peroxide and malonaldehyde contents. Increased proline content and enzymatic antioxidants were found to alleviate oxidative damage under cold stress. Yukon-R showed significantly higher proline content, and enzymatic antioxidant activities than A4177G3-RIB when the temperature was lower than 10°C. Furthermore, the role of phospholipids, particularly phosphatidic acid (PA) in cold tolerance was investigated. Lipidomic results showed that the membrane lipids phosphatidylcholine and phosphatidylglycerol levels were decreased in contrast to increased levels of phosphatidylethanolamine and PA under cold temperatures. Specifically, Yukon-R showed significantly higher PA, phosphatidylcholine and phosphatidylglycerol contents than A4177G3-RIB in both leaf and root membranes under cold conditions, suggesting their positive roles (stress signaling transduction, maintaining cellular integrity and photosynthetic processes, respectively) in cold tolerance. Taken together, the study suggests that: (i) Yukon-R could be considered a potential candidate genotype to be grown in the boreal climate; (ii) phospholipid remodeling and PA accumulation in leaf and root are required for silage corn cold stress acclimation at the early growth stage.

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