Study On The Mechanism Of Exogenous Application Of Calcium Ions To The Resistance Of Pear Ring Rot And The Bioinformatics Of PbrATG8 Family

Pear ring rot,caused by Botryosphaeria dothidea,is one of the most serious diseases in pear.Calcium(Ca2+)was reported to play a key role in the plant defense response.Here,we found that exogenous calcium could enhance resistance to B.dothidea in pear leaves.Less H2O2 and O2-but more activated ROS-scavenge enzymes accumulated in calcium treated leaves than in H2O-treated leaves.Moreover,the increased level of more AsA-GSH was maintained by Ca2+treatment under pathogen infection.The expression of core autophagyrelated genes and autophagosome formations were enhanced in Ca2+-treated leaves.Moreover,the salicylic acid(SA)level and SA-related gene expression were induced more strongly by B.dothidea in Ca2+-treated leaves than in H2O-treated leaves.Taken together,these results demonstrated that exogenous Ca2+ enhanced resistance to B.dothidea by increasing autophagic activity and SA accumulation.Our findings reveal a new mechanism of Ca2+in increasing the tolerance of pear to B.dothidea infection.Autophagy plays an important role in plant growth,development and stress tolerance.ATG8 has been reported to be an autophagy marker in many species.However,there is little information about ATG8 family members in pear(Pyrus bretschneideri).We performed a genome-wide analysis and identified 9 PbrATG8 gene family members in pear.Phylogenetic analysis showed that PbrATG8 genes clustered into three major groups(Groups Ⅰ-Ⅲ).Eight PbrATG8 genes were mapped to 6 chromosomes.The synteny results showed that two pairs were collinear.Furthermore,gene expression data showed that all genes were differentially expressed in a range of pear tissues.The transcript analysis of PbrATG8 genes under drought,salt and pathogen infection stresses revealed that PbrATG8c may play an important role in the stress response.The PbrATG8c protein was localized in the nuclear and membrane,and silencing of PbrATG8c decreased the resistance to Botryosphaeria dothidea in pear.This study provides insight and rich resources for subsequent investigations of autophagy in pear.Nine PbrATG8s were identified in pear genome,each with a highly conserved Atg8 domain.Gene structure and motif analysis revealed the diversity of PbrATG8 family.Expression patterns showed PbrATG8c may play an important role in the stress response.The PbrATG8c protein was localized in the nuclear and membrane.Silencing of PbrATG8c reduced the resistance to pathogen infection in pear indicating the positive role of PbrATG8c in pathogen resistance...