Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/25/2010
Publication Date: 9/27/2010
Citation: Chen, J., Xu, W., Burke, J.J., Xin, Z. 2010. Role of phosphatidic acid in high temperature tolerance in maize. Crop Science. 50(6):2506-2515. Interpretive Summary: High temperature (HT) stress severely limits plant productivity and causes extensive economic loss to US agriculture. Two inbred lines, HT-tolerant B76 and HT-sensitive B106, were selected from a diverse collection of germplasm to conduct detailed physiological and biochemical study to identify biological components critical to HT tolerance. The difference in HT tolerance between the two inbred lines was confirmed under controlled environment. Membrane thermostability, as determined by electrolyte leakage and quantum yield of PSII, was found to be a factor accounting for the difference in thermotolerance between the two inbred lines. Membrane lipid profiling identified that a signaling lipid species, phosphatidic acid (PA), was induced by high temperature treatment and that the levels of PA is closely correlated with HT tolerance of these two lines. The result indicates that membrane thermostability play an important role in HT tolerance in maize and proper level of PA is crucial to maintain membrane stability under HT stress. The discovery may lead to new ways to improve heat tolerance in maize
Technical Abstract: Maize (Zea mays, L.) germplasm exhibits large genetic variations in tolerance to high temperature (HT) stress under field conditions, but the mechanisms underling this variation are largely unknown. Based on many years of field observation, maize inbred line B76 consistently displays better tolerance to HT than B106. Heat waves during growing season cause leaf firing in developing leaves and tassel blasting in B106 but not in B76. The difference in HT tolerance between the two inbred lines was confirmed in growth chambers under controlled conditions. The two inbred lines showed similar level in the induction of heat shock proteins and a chloroplast elongation factor (EF-Tu), two mechanisms known to involve in HT tolerance in maize. A drastic decrease in PSII quantum efficiency occurred at 34-35°C in B106, in B76, it occurred at a much higher temperature (>38°C). Cell membranes of B76 appeared to be more stable under HT than those of B106 based on electrolyte leakage analysis. Lipid profiles of young developing leaves by lipidomics showed that, among all lipids detected, only phosphatidic acid (PA) exhibited significant higher level in B76 than in B106 under both normal and HT stressed conditions (P<0.02). Moreover, PA was the only lipid that was significantly increased by HT treatment (P<0.05). Our results suggest that membrane thermostability is essential to HT tolerance and that PA may play an important role in imparting membrane thermostability, and hence, HT tolerance in maize.