HC-Pro Disrupts miR319-TCP Regulatory Pathways to Induce Sterility in Transgenic Plants.

Helper component-proteinase (HC-Pro), encoded by tobacco vein banding mosaic virus (TVBMV), can cause various viral symptoms and even abortion. HC-Pro counteracts host-mediated inhibition by interfering with the accumulation of microRNAs (miRNAs) and small interfering RNAs (siRNAs). However, it is unclear whether the abortion phenotype of transgenic plants expressing HC-Pro is related to the abnormal expression of TEOSINTE BRANCHED 1/CYCLOIDEA/PROLIFERATING cell factors (TCPs), which are involved in regulating fertility. In this study, the molecular mechanisms through which HC-Pro causes various sterile phenotypes in plants were investigated. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Northern blotting revealed that in HC-Pro transgenic plants, the expression levels of TCP4 and TCP24 significantly increased. The increased expression of TCP4 further upregulated LIPOXYGENASE2 (LOX2), a gene encoding a key enzyme in the synthesis of jasmonic acid (JA) precursors. Further studies confirmed that the aberrant expression of TCP3, TCP4 and TCP24 blocks the elongation of petals and anthers and that the aberrant expression of TCP4 and TCP24 blocks the release of pollen. This study demonstrated that HC-Pro affects the expression levels of the miR319-targeted genes TCP2, TCP3, TCP4, TCP10 and TCP24, thereby affecting the normal development of floral organs and resulting in plant abortion. Both tobacco and Arabidopsis thaliana were used as model systems in this study on virus-mediated fertility, which provides important information for understanding how viral pathogenicity affects the regulation of fertility in crops.