Functional Analysis Of The Auxiliary Molecular Chaperone BAG Proteins In Disease Resistance In Tomato

Botrytis cinerea is a kind of saprophytic fungi with a necrotrophic nutritional lifestyle which can infects hundreds of monocotyledons and dicotyledons and causes gray mold disease,so that it is harmful for crop production,vegetable quality and fruit preservation.In this study,we used virus-induced gene silencing(VIGS)technology to explore the functions and possible mechanism of molecular chaperone proteins SIBAGs in disease resistance against Botrytis cinerea in tomato.Molecular chaperones play an important role in protein folding,protein quality control,assembly of multi-subunit protein complexes and transport of proteins.BAG(Bcl-2-associated athanogene)family is an evolutionally conserved family of chaperone regulators,and its homologues have been found in plants,animals and yeast.BAGs have a conserved structure and have been shown to regulate,both positively and negatively,the function of Hsp70/Hsc70 chaperones,and modulate diverse physiological processes through forming functional complexes with a range of transcription factors and signaling proteins.The study of BAG family in mammals began earlier and has been very extensive and in-depth.7 members of AtBAGs have been identified in Arabidopsis thaliana,which not only regulate plant resistance to saprophytic fungi,but also regulate plant growth and development.Previous studies have also reported that members of the BAG family in rice can regulate disease resistance to saprophytic fungi.However,the role of BAG family proteins in disease resistance or growth and development of tomatoes is still unclear.In this study,we identified and cloned 10 SIB AG chaperone genes in tomato genome database by bioinformatics method.Conserved domain analysis showed that all the 10 tomato SlBAG proteins contained a conserved BAG domain and they locate in mitochondrion,chloroplast,and nucleus.Silencing 10 SIB AG chaperone genes in tomato by VIGS technique and inoculating silent plants with B.cinerea show that silencing of SlBAG5 enhanced plant resistance to Botrytis cinerea.We found that over-expression of SlBAG5 can induce the accumulation of reactive oxygen species and cell death by transient overexpression technology or virus-induced gene overexpression techbology.Quantitative real-time PCR analysis identified that silence and overexpression of SlBAG5 also affect the expression levels of JA/ET pathway-related genes(SINR1,SlLapAl,SIMYC2 and SLJAZ7)and SA pathway-related genes(SlPRlb,SlPRP2)induced by B.cinerea.Lastly,we detected that the silence and overexpression of SlBAG5 could alter the PTI response mediated by chitin,such as the production of ROS and the expression levels of PTI-related genes SlPTI5,SILRR22 and SIWRKY28 by Lumino chemiluminescence method.In addition,we found 8 interacting proteins of SlBAG5 by searching yeast screening library,and verified their interaction by BiFC,Co-IP or other methods.