Discovery of BrATG6 and its potential role in Brassica rapa L. resistance to infection by Plasmodiophora brassicae

Clubroot disease, caused by Plasmodiophora brassicae infection, occurs in cruciferous vegetable crops in many areas of the world, sometimes leading to yield loss. In this study, a differentially expressed protein (0305), was found between control and clubroot-diseased Chinese cabbage (Brassica rapa L.) roots through two-dimensional electrophoresis. Mass spectrometry analysis showed that Bra003466 was highly matched to protein 0305. Because the sequence of Bra003466 had 89% percent identity with ATG6 of Arabidopsis thaliana and other Brassica, the gene was named as BrATG6. However, 790 bp sequences were mismatched with the cDNA sequence of the Bra003466 gene from the Brassica database. In this study, we cloned the cDNA of Bra003466 and found the BrATG6 was highly expressed in roots among all organs. When plants were inoculated with P. brassicae Woronin, the expression of BrATG6 was significantly increased in infected roots of Chinese cabbage. This result was verified by reverse transcription-qPCR and in situ hybridization. Examination of disease resistance showed that, compared with wild type plants, A. thaliana ATG6 deletion mutants were more easily infected by P. brassicae than WT. This shows that BrATG6 may play a potential role in the resistance of B. rapa to P. brassicae infection.