The regulation of autophagy of susceptible Nicotiana tabacum under tobacco mosaic virus infection
Autophagy (or self-eating) is an important conserved process by which eukaryotic cells recycle intracellular components. This study was undertaken to elucidate whether tobacco mosaic virus (TMV) infection on tobacco plants induced autophagy. TMV-U1 and its susceptible host Nicotiana tabacum cv. Blight yellow was used in this study. Transmission electron microscope (TEM), monodansylcadaverin (MDC) staining, an autophagosome marker enhanced cyan fluorescent protein (ECFP)–tagged tobacco ATG8f (ECFP-ATG8f), real-time fluorescent quantitative (qRT-PCR) and real-time fluorescent quantitative (qRT-PCR) assay were used to investigate the formation of autophagic structures, acidic compartments, and the transcript levels of autophagy related genes, including ATG3, ATG4, ATG5, ATG6, ATG7, ATG8a and ATG18a, in tobacco plants infected by TMV, respectively. A number of autolysosome-like structures were observed in the cytoplasm and vacuole of tissue in 72 hpi by TEM. Strong punctate MDC-stained autolysosomes in the cells were observed in the cells in 72 hpi. The expression levels of all these ATG genes, except for ATG5, were increased at 48 hours post inoculation (hpi), and peaked at 72 hpi. These results suggest that TMV infection induced cell autophagy of the susceptible host tobacco.