Expression Characteristics of CsPAE55 in Citrus and Analysis of Its Interacting Protein

Abstract

Exploring the resistance genes of citrus to Huanglongbing (HLB) is the foundation and key to disease resistance breeding. Based on comparative genomic transcriptome data, four pectin acetylesterase (PAE) genes responsive to Candidatus liberibacter asiaticus (CaLas) infection induction were screened, and a gene cloned with higher differential expression levels was identified, named CsPAE55. Bioinformatics analyses showed that CsPAE55 was conserved but had sequence differences compared with homologs. The subcellular localization results of tobacco indicated that CsPAE55 protein was mainly localized in the nucleus and cytoplasm. RT-qPCR analysis showed that the expression of CsPAE55 was related to variety tolerance, tissue site, and symptom development. In addition, we established virus vector-mediated infection systems in citrus, namely gene silencing systems mediated by virus-induced gene silencing (VIGS) and gene overexpression systems mediated by citrus leaf blotch virus (CLBV), and obtained CsPAE55 silencing and overexpression plants. And we established a stable transformation system mediated by Agrobacterium rhizogenes in citrus and obtained CsPAE55 silencing and overexpression citrus hairy roots. The analysis of hormone content and gene expression in CsPAE55 plants also indicated that overexpression of CsPAE55 regulated the transcriptional regulation of genes involved in systemic acquired resistance (SAR) response. Using Protein–Protein Interaction (PPI) to predict and screen for a citrus protein CsARF1 that may interact with CsPAE55, and preliminarily verifying its interaction with CsPAE55 protein through Yeast Two-hybrid (Y2H) and Bimolecular Fluorescent Complimentary (BIFC). In summary, our data provided theoretical basis and genetic resources for subsequent molecular breeding of citrus resistance to HLB disease.