DROUGHT STRESS: Role of Carbohydrate Metabolism in Drought‐Induced Male Sterility in Rice Anthers*

Abstract

Rice plants exposed to three consecutive days of water stress (−0.5 MPa) show a reduction in male fertility and grain set, which is attributed to increased levels of reactive oxygen species (ROS) and activation of a programmed cell death. This current research was conducted to further investigate the association of sugar metabolism with microspore abortion in rice anthers. Biochemical assays showed that sucrose, glucose and fructose contents were found to be significantly increased in anthers from water stressed plants compared with the control. qRT‐PCR analyses and in situ hybridization of metabolic genes (sugar transporters, invertase and phosphotransferase/kinases) demonstrated that the supply of sugars for developing microspores and the initial steps of sugar utilization e.g. glycolysis, were not repressed. However, it appears that the accumulation of sugars in stressed anthers might involve a reduction of mitochondrial activity during the tricarboxylic acid cycle, which could result in excessive production of ROS and a depletion of the ATP pool. These results also suggest that higher levels of sugars at all stages of anther development seemed to be associated with some measure of protection to the anthers against oxidative stress. Induced expression of sugar transporter genes might have maintained the high levels of sugar in the tapetum and the locules, which alleviated oxidant damage caused by excessive ROS generation. Thus, the increased level of sugars might potentially be a natural response in providing protection against oxidant damage by strengthening the antioxidant system in anthers.

The effect of high temperature stress on male and female reproduction in plants

“…Metabolism during the uninucleate stage generates substantial reactive oxygen species (ROS) in anther tissues, with the highest levels occurring in the tapetum and microspores. ROS scavenging antioxidants are essential to maintain an environment where ROS contribute to integration of development under ambient conditions (Cheeseman, 2007;Nguyen et al, 2009;Frank et al, 2009;Nguyen et al, 2010;Ariizumi and Toriyama, 2011;Mittler et al, 2011;Hu et al, 2011;Zhang et al, 2012;Bagha, 2014). Mutations in genes encoding proteins involved in carbohydrate assimilation, synthesis and secretion of proteins and lipids, ROS homeostasis, and pollen wall synthesis result in uninucleate microspore abortion (Ma, 2005;Ariizumi and Toriyama, 2011;Wilson et al, 2011;Hu et al, 2011).…”

“…High temperature stress results in changes in carbohydrate metabolism in Capsicum (Aloni et al, 2001) and Sorghum anthers that includes reduced expression of cell wall invertase genes in Sorghum tapetum and pollen (Jain et al, 2007(Jain et al, , 2010 and reduced cell wall invertase activity in Capsicum pollen (Aloni et al, 2001). Cold and drought stress imposed at the microspore stage of pollen development also results in downregulation of cell wall invertases and monosaccharide transporter genes in the tapetum of wheat and rice (Dorion et al, 1996;Sheoran and Saini, 1996;Ji et al, 2011;Nguyen et al, 2010). The negative impact of HT and other stresses on the timing of tapetal cell death and tapetal invertase activity is proposed to limit provisioning of compounds, to include hexose, to developing pollen and it has been hypothesized that this results in microspore starvation and subsequently, abortion (Parish et al, 2012;De Storme and Geelen, 2014).…”

Drought Stress Responses in Plants, Oxidative Stress, and Antioxidant Defense

“…Exogenous Se in drought-stressed rapeseed seedlings (B. napus cv. The reproductive stage is extremely sensitive to drought stress [137,234]. Under both mild and severe drought stress the activities of DHAR, GST, and GPX significantly increased, and CAT activity decreased.…”

Identification of Amplified Fragment Length Polymorphism (AFLP) Markers Tightly Associated with Drought Stress Gene in Male Sterile and Fertile Salvia miltiorrhiza Bunge

“…This indicates that fertile NIL population of S. miltiorrhiza loses its fertility after one-month severe drought stress when meiosis and the young microspore stage are included. During meiosis and at the young microspore stage the tapetum is metabolically extremely active [15], but would cause a premature cell death (PCD) response when meeting drought stress [16]. In male gametophyte of male sterile S. miltiorrhiza , tapetal hypertrophy was observed as well as the delayed natural programmed cell death [8].…”