Genome-Wide Identification Of The BTB Domain-Containing Protein Gene Family And Characterization Of The Related Genes Under Phytophthora Capsici Infection And Abiotic Stresses In Pepper(Capsicum Annuum L.)

Pepper(Capsicum annuum L.)is an important vegetable crop worldwide.The production of pepper is severely threatened by a variety of diseases,especially the soil borne Phytophthora blight which is caused by Phytophthora capsici.So it is of great importance to identify and study the genes related to P.capsici for breeding of blight resistance cultivars in pepper.The BTB genes are important stress related genes which have been studied in many crop species such as Oryza sativa,Arabidopsis thaliana,Solanum lycopersicum,Zea mays,and Triticum aestivum.These genes function in a variety of cellular contexts ranging from transcriptional regulation to protein ubiquitination and degradation,playing significant roles in response to pathogens infection and abiotic stresses.In this study,we identified and analyzed the BTB protein family members in pepper genome.Also,the function of three members of BTB-MATH subfamily and a transcription factor CanTF in pepper under Phytophthora capsici infection and abiotic stresses were characterized.The main findings of the study are as below:1.54 BTB protein family members in the pepper genome were identified,which were distributed on the 12 chromosomes of pepper.The BTB proteins can be divided into many subfamilies,such as BTB-TAZ,BTB-MATH,and BTB-NPH3 etc.Pepper BTB genes specifically expressed in different tissues and were induced by biotic stress,i.e.the Phytophthora capsici infection2.All the five members of BTB-MATH subfamily were induced by Phytophthora capsici(PC and HX-9 strains)infection.CaBTB4 and CaBTB18 were down-regulated while CaBTB2,CaBTB27,and CaBTB51 were up-regulated3.The subcellular location of pepper CaBPM4 was on the plasma membrane.CaBPM4(CaBTB51)was not only induced by the Phytophthora capsici infection,but also was induced by abiotic stresses,such as cold,drought,and salt stresses.Silencing of CaBPM4 weakened the pepper defense response through negatively affecting the expression of defense-related gene(CaPR1,CaDEF1,CaSAR82,and CaPO1).However,silencing of CaBPM4 enhanced the defense response of pepper against abiotic stresses,namely salt and drought stresses.4.CaBTB27 was up-regulated under Phytophthora capsici infection and abiotic stresses as well as ABA and ET applications.Silencing of CaBTB27 in pepper plants weakened the pepper defense response to P.capsici with a lower expression of defense-related genes,and lower root activity under P.capsici infection.However,silencing of CaBTB27 enhanced tolerance to salt,drought,and cold stresses5.CaBTB2 showed up-regulated expression pattern under P.capsici infection and abiotic stresses as well as ABA and ET applications.Silencing of CaBTB2 in pepper plants weakened the defense response to P.capsici while enhanced the pepper tolerance against salt and cold stresses.6.The transcription factor CanTF was up-regulated under P.capsici infection and abiotic stresses as well as SA and H2O2 applications.Silencing of CanTF in pepper plants weakened the defense response to P.capsici infection as well as to salt,cold,and drought stresses.