OsNAL11 and OsBURP12 Affect Rice Seed Germination at Low Temperature.

Cold stress is one of the major disasters that severely affect agricultural production. Heat shock protein 40 (HSP40) and BURP proteins are involved in the cold stress response. However, the physiological and molecular mechanisms of heat shock proteins and BURP family proteins regulating seed germination at low temperature are rarely reported. Under low temperature stress, the seed germination rate, germination index and germination potential of nal11 and burp12 mutants were lower than those of the wild type (ZH11), and the seedlings grew slowly. The interaction between OsNAL11 and OsBURP12 was confirmed by yeast two-hybrid, Split-LUC, BiFC and Co-IP assays. Further analysis revealed that compared with ZH11, nal11 and burp12 mutants had reduced reactive oxygen species scavenging ability during low-temperature germination. Meanwhile, the nal11 and burp12 mutants had higher endogenous ABA levels and exhibited lower PG (polygalacturonase) activity and higher pectin content during low-temperature germination. These results suggest that OsNAL11 and OsBURP12 are likely to regulate seed germination under low temperature mainly by modulating endogenous ABA levels and cell wall modification, which deepens the understanding of the regulation mechanism of rice seed germination under low temperature stress.