Study On The Functions Of Histone Deacetylases(HDACs)in Response To Temperature Stresses In Tomato

The environment temperature in facility cultivation often changes drastically.Extreme high temperature and low temperature have become the main environmental factors limiting the growth and development of tomato(Solarium lycopersicum)and other facilities.Histone acetylation modification is one of the important epigenetic regulation mechanisms involved in gene expression,and is closely related to plant growth and development and stress response.Histone deacetylases(HDACs)play a major role in deacetylation and play important roles in stress responses such as drought and salt stress.However,their roles in temperature stress are unclear.Therefore,it is of great theoretical and practical significance to study the roles of histone deacetylases(HDACs)in response to temperature stresses and the underlying mechanisms in tomato.This paper uses tomato as experimental material.Some of HDACs were screened by gene expression analysis in temperature stresses.The regulation of HDACs in response to temperature stresses was studied by virus-induced gene silencing(VIGS),and the relationship between the function of HDACs and the signal pathway of abscisic acid(ABA)and brassinosteroid(BR)was elucidated.The main findings obtained are as follows:1.It was clear that the functions of HDACs gene family were differentiated in response to heat stress.By aligning with HDACs in Arabidopsis thaliana,HDACs in tomato were identified and a phylogenetic tree was constructed.After heat treatment,HDA4,HDA5,HDA6,HDA10,HDT2 and SRT1 were significantly up-regulated.It was speculated that these six genes responded to heat stress in tomato.By the virus-induced gene silencing(VIGS),we obtained HDA4,HDA5,HDA6,HDA10 HDT2 and SRT1 gene silenced plants,respectively.Photochemical efficiency and electrolyte penetration indicated that silencing HDA4 or HD A 5 resulted in increased heat tolerance,while silencing HDT2 or SRTI resulted in decreased heat tolerance in tomato.The ABA content of SRT1 gene silenced plants was significantly lower than that of the control.Meanwhile,only the ABA content of SRT1 gene silenced plants was significantly different from the control.The above results indicated that SRT1 may positively regulate heat tolerance by affecting the metabolism of ABA in tomato.However,the regulatory mechanisms of HDA4,HDA5 and HDT2 were still unclear and needed further study.2.It was clarified that SRT1 could improve cold tolerance of tomato by regulating the metabolism of ABA.In the process of cold treatment,the relative expression of SRT1 was significantly up-regulated.It was speculated that it responded to cold stress in tomato.By the VIGS technique,we obtained SRT1 gene silenced plants.Photochemical efficiency and electrolyte penetration indicated that silencing SRT1 resulted in decreased cold tolerance in tomato.Compared with the control,the ABA content of SRT1 gene silenced plants was significantly decreased.At the same time,the expression levels of ABA synthesizing genes NCED1 and NCED2 in SRT1 gene silenced plants were significantly decreased,while the expression of ABA degradation gene CYP707A2 was significantly increased.The above results indicated that SRT1 might increase the ABA content by inhibiting the expression of CYP707A2 and promoting the expression of NCED1 and NCED2 to positively regulate cold tolerance in tomato.3.The relationship between SRT1 and BR signaling pathway in regulating cold tolerance of tomato was clarified.Using tobacco transient overexpression,it was found that SRT1 was only localized in the nucleus.By yeast two hybrid and biomolecular fluorescence complementation,it was clarified that transcription factor BZR1 in BR signaling pathway and SRT1 could interact with each other and colocalized with the nucleus.After cold treatment,the crispr gene editing mutants of BZR1 were weaker than that of the control in cold tolerance,while cold tolerance of the BZR1-overexpressed plants were stronger than that of the control.The result indicated BZR1 positively regulated cold tolerance in tomato.By using VIGS technique,SRT1 was silenced in CR and OE-BZR1-17-3#,respectively.We obtained pTRV-TRV(CR),pTRV-SRT1(CR),pTRV-7TRV(OE-BZR1-17-3#)and pTRV-SRT1(OE-BZR1-17-3#).After cold treatment,photochemical efficiency and electrolyte penetration indicated that pTRV-TRV(OE-BZR1-17-3#)had the strongest cold tolerance,but BZR1-mediated cold tolerance completely disappeared due to the silence of SRT1.The content of ABA was consistent with cold tolerance.The ABA content of pTRV-TRV(OE-BZR1-17-3#)was the highest in cold stress,while the ABA content was significantly decreased after silencing SRTI.This was related to the down-regulation of ABA synthetic genes NCEDl and NED2,and the up-regulation of ABA degradation gene CYP707A2.The above results indicated that the histone deacetylase SRT1 not only directly regulated the expression of ABA degradation gene(CYP707A2),but also interacted with BZR1 to regulate the expression of ABA synthesis genes(NCED1?NCED2),which increased the ABA content in the plants to increase cold tolerance of tomato.