Study On The Molecular Function Of TFL2/LHP1 In High Temperature Response Pathway

Temperature is one of the main environmental factors that restrict crop yield and quality.With global warming,the yield of food crops is gradually decreasing.Therefore,it is urgent to study the mechanism of high temperature response in plants.Studies have shown that epigenetics plays an important role in regulating plant growth and stress response.In this study,epigenetic-associated mutants were screened by high temperature treatment.It was found that the only HP1(Heterochromatin Protein 1)homologue TFL2/LHP1 in Arabidopsis is involved in high temperature response.This study initially explored the function of TFL2/LHP1 in the high temperature response pathway.The main results are as follows:(1)Under 28? treatment,it was found that the hypocotyl of tfl2 can not elongate significantly.The hypocotyl cells also did not elongate.To further validate the phenotype of TFL2/LHP1 in the high-temperature response pathway,this study constructed a tfl2 complementation line,it can restore the phenotype of tfl2 under high temperature conditions.The above results suggest that TFL2/LHP1 is involved in high temperature response and is associated with high temperature induced hypocotyl elongation.(2)HSP70(Heat Shock Protein 70)is associated with plant heat tolerance,and the expression of HSP70 gene is elevated by the regulation of histone variant H2 A.Z at high temperature.After high temperature treatment for 0~12 h,the expression of HSP70 gene in Col and tfl2 was not significantly up-regulated.After 24~48 h of high temperature treatment,the expression of HSP70 gene in Col and tfl2 was significantly up-regulated,but the increase in tfl2 was lower than that in Col.The above results suggest that TFL2/LHP1 may not participate in the rapid response to high temperature processes,but play an important role in the process of plants adapting to high temperatures.Studies have shown that both PIF4(Phytochrome-Interacting Factor4)and TFL2/LHP1 can directly bind to the promoter of the auxin synthesis gene YUCCA8 and regulate its expression.This study found that after high temperature treatment,compared with Col,the expression of PIF4 increased in tfl2 plants,but the expression of YUCCA8 was not increased significantly.These results suggest that TFL2/LHP1 may regulate the expression of YUCCA8 gene by affecting PIF4,thereby regulating hypocotyl elongation at high temperatures.(3)Yeast two hybrid experiments showed that TFL2/LHP1 could not interact with PIF4,it is speculated that TFL2/LHP1 may cooperate with other proteins to participate in the high temperature response pathway.Therefore,this study screen yeast library to find related proteins andfinally obtained 31 candidate proteins,including the key gene of GA synthesis CYP701A3,the repressor protein of JA signal transduction pathway JAZ5 and NF-YB13,which provides a reference for further research on how TFL2/LHP1 regulates the phytohormone network to response high temperature.