Abstract
Spring flowers such as barley and Arabidopsis are more sensitive to high-temperature stress, and summer flowers including rice are susceptible to low-temperature stress. Severe injuries by the stresses commonly appeared during pollen development, and these result in male sterility. Despite lots of previous histological and physiological studies, molecular mechanisms are not still clear. We therefore focused on the expression of phytohormone-related genes, and the results implied that two phytohormones, auxin and gibberellin respectively play an important role in high- and low-temperature injury. Increasing temperatures repressed the expression of auxin biosynthesis genes in barley and Arabidopsis developing anther cells. Moreover, endogenous auxin reduced in anther specific manner. Finally, we found that exogenous auxin could restore male sterility caused by high-temperature injury. In the case of rice plants, gibberellin insensitive mutants became hyper-sensitive to low-temperature stress, indicating that gibberellin functions as tolerance to low-temperature stress. These results are useful for promotion and maintenance of crop yields under the global climate change.
