Effects of elevated air temperature coupling with soil drought on carbohydrate metabolism and oil synthesis during cottonseed development

Abstract

Cotton, as the fifth-largest oilseed crop, often faces the coupling stress of heat and drought. Still, the effects of combined stress on cottonseed oil synthesis and its closely related carbon metabolism are poorly investigated. To this end, experiments were conducted with two cultivars (Sumian 15 and PHY370WR) under two temperature regimes: ambient temperature (AT) and elevated temperature (ET, which was 2.5 C-2.7 C higher than AT) and three water regimes: optimum soil moisture (soil relative water content [SRWC] at 75% ± 5%), and drought (SD) including SRWC 60% ± 5% and SRWC 45% ± 5%, during 2016-2018. Results showed that ET plus SD decreased cottonseed kernel yield, seed index, kernel weight, and kernel percentage more than either single stress. The content of hexoses, the carbon skeleton source for oil synthesis, was decreased by ET while increased by SD. The combined stress increased the hexose content by increasing the activities of sucrose synthase (SuSy, EC 2.4.1.13) and invertase (Inv, EC 3.2.1.26) and upregulating GhSuSy expression; however, hexose content under combined stress was lower than that under SD alone. Increased oil content under SD was attributed to the high phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31), acetyl-CoA carboxylase (ACCase, EC 6.4.1.2), and diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) activities, whereas the opposite effects were seen under ET. Under combined stress, although ACCase activity decreased, PEPCase and DGAT activities, and GhPEPC-1 and GhDGAT-1 expression upregulated, enhancing carbon flow into oil metabolism and triacylglycerol synthesis, ultimately generating higher oil content. | INTRODUCTIONAgricultural production has been seriously affected by heat and drought stresses due to global warming (IPCC, 2014). The ongoing climate change is predicted to cause a 2.8 C ± 0.4 C increase in the global surface temperature by the end of the 21st century and to augment the intensity and frequency of water-deficit stress events (Brown & Caldeira, 2017). It is possible that in important cropproducing regions, yields will decline sharply in the future due to global warming and changing precipitation patterns (Juroszek et al., 2020). Cotton is an important crucial cash/oilseed crop, and China is the second-largest country for cotton production. China's cotton yield per unit area is more than double the world average (OECD/FAO, 2020). However, the cotton belts in China are largely located in arid and semi-arid areas. Heat and drought events often cooccur in summer and autumn, a period coinciding with the flowering Bingjie Xu and Wei Hu contributed equally to this study.

Drought Stress and High Temperature Affect the Antioxidant Metabolism of Cotton (Gossypium hirsutum L.) Anthers and Reduce Pollen Fertility

“…Different soil-moisture treatments began at the early stage of flowering. When the soil moisture reached the predetermined level, the temperature treatments were established (Figure S1) according to our previous report [10], using a Temperature Control System (OTC, Southeast Co., Ltd., Ningbo, China) to raise the ambient temperature 2-3 • C. The mean daily temperatures in the ambient and the elevated temperature areas in 2019 and 2020 are shown in Table S1. The mean daily temperature in the ambient temperature area in 2019 and 2020 were 31.7 • C and 31.2 • C, respectively, lower than the upper limit of 32 • C of the optimum temperature range for cotton development [37].…”

“…Drought is also the main abiotic stress factor that limits crop growth, especially drought occurring at the flowering and boll-forming stage, leading to a significant decrease in pollen fertility, which is not conducive to fertilization and fruiting [6], therefore reducing the crop yield [7,8]. Moreover, heat and drought stresses usually occur simultaneously under field conditions, and some studies have explored the effects of combined stress of drought and heat temperature on the physiological and metabolic activities in cotton (Gossypium hirsutum L.) leaves, fibers, and seeds [9,10]. However, there are few studies on the effects of the combined stress of drought and high temperature on the physiological and metabolic activities of cotton male organs and their relationship with pollen fertility.…”

Response mechanism of carbon metabolism of Pinus massoniana to gradient high temperature and drought stress

“…Moreover, investigations into sucrose and starch metabolism have revealed that high-temperature treatment can increase the sucrose content in plants [ 14 ]. Under conditions of drought or high-temperature drought, both sucrose and starch contents decrease significantly, indicating that drought activates plant's ability to degrade sucrose [ 15 ]. The influence of high temperature and drought on plant starch remains controversial.…”

Unraveling the metabolic profile regulation of camellia oilseeds under insect and heat stress: Insights into functional effects and mechanistic basis

“…Apart from pre-harvest insect stresses, oilseeds are also susceptible to post-harvest heat stresses, particularly during the processing stage ( Oliete, Lubbers, Fournier, Jeandroz, & Saurel, 2022 ; Xu et al, 2022 ; D. Zhu, Guan, Fan, Sun, & Wang, 2022 ). The functional health components of oilseeds are also often destroyed by these insect/heat stresses, which lessens the oilseeds' health benefits and economic value ( Memoli et al, 2017 ; Valencic, Butinar, Podgornik, & Bucar-Miklavcic, 2021 ).…”