AUTHOR=Rahman Hafizur , Xu You-Ping , Zhang Xuan-Rui , Cai Xin-Zhong 

TITLE=Brassica napus Genome Possesses Extraordinary High Number of CAMTA Genes and CAMTA3 Contributes to PAMP Triggered Immunity and Resistance to Sclerotinia sclerotiorum

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00581

DOI=10.3389/fpls.2016.00581

ISSN=1664-462X

ABSTRACT=<p>Calmodulin-binding transcription activators <italic>(CAMTAs)</italic> play important roles in various plant biological processes including disease resistance and abiotic stress tolerance. Oilseed rape (<italic>Brassica napus</italic> L.) is one of the most important oil-producing crops worldwide. To date, compositon of <italic>CAMTAs</italic> in genomes of <italic>Brassica</italic> species and role of <italic>CAMTAs</italic> in resistance to the devastating necrotrophic fungal pathogen <italic>Sclerotinia sclerotiorum</italic> are still unknown. In this study, 18 <italic>CAMTA</italic> genes were identified in oilseed rape genome through bioinformatics analyses, which were inherited from the nine copies each in its progenitors <italic>Brassica rapa</italic> and <italic>Brassica oleracea</italic> and represented the highest number of <italic>CAMTAs</italic> in a given plant species identified so far. Gene structure, protein domain organization and phylogentic analyses showed that the oilseed rape <italic>CAMTAs</italic> were structurally similar and clustered into three major groups as other plant <italic>CAMTAs</italic>, but had expanded subgroups <italic>CAMTA3</italic> and <italic>CAMTA4</italic> genes uniquely in rosids species occurring before formation of oilseed rape. A large number of stress response-related <italic>cis</italic>-elements existed in the 1.5 kb promoter regions of the <italic>BnCAMTA</italic> genes. <italic>BnCAMTA</italic> genes were expressed differentially in various organs and in response to treatments with plant hormones and the toxin oxalic acid (OA) secreted by <italic>S. sclerotiorum</italic> as well as the pathogen inoculation. Remarkably, the expression of <italic>BnCAMTA3A1</italic> and <italic>BnCAMTA3C1</italic> was drastically induced in early phase of <italic>S. sclerotiorum</italic> infection, indicating their potential role in the interactions between oilseed rape and <italic>S. sclerotiorum</italic>. Furthermore, inoculation analyses using Arabidopsis <italic>camta</italic> mutants demonstrated that <italic>Atcamta3</italic> mutant plants exhibited significantly smaller disease lesions than wild-type and other <italic>Atcamta</italic> mutant plants. In addition, compared with wild-type plants, <italic>Atcamta3</italic> plants accumulated obviously more hydrogen peroxide in response to the PAMP chitin and exhibited much higher expression of the CGCG-box-containing genes <italic>BAK1</italic> and <italic>JIN1</italic>, which are essential to the PAMP triggered immunity (PTI) and/or plant resistance to pathogens including <italic>S. sclerotiorum</italic>. Our results revealed that <italic>CAMTA3</italic> negatively regulated PTI probably by directly targeting <italic>BAK1</italic> and it also negatively regulated plant defense through suppressing JA signaling pathway probably via directly targeting <italic>JIN1</italic>.</p>