In BPS1 Downregulated Roots, the BYPASS1 Signal Disrupts the Induction of Cortical Cell Divisions in Bean-Rhizobium Symbiosis.

BYPASS1 (), which is a well-conserved gene in plants, is required for normal root and shoot development. In the absence of gene function, overproduces a mobile signalling compound (the signal) in roots, and this transmissible signal arrests shoot growth and causes abnormal root development. In addition to the shoot and root meristem activities, the legumes also possess transient meristematic activity in root cortical cells during symbiosis. We explored the role of during nodule primordium development using an RNA-interference (RNAi) silencing approach. Our results show that upon infection, the transgenic roots failed to induce cortical cell divisions without affecting the rhizobia-induced root hair curling and infection thread formation. The transcript accumulation of early nodulin genes, cell cyclins, and cyclin-dependent kinase genes was affected in RNAi lines. Interestingly, the root nodule phenotype was partially rescued by exogenous application of fluridone, a carotenoid biosynthesis inhibitor, which was used because the carotenoids are precursors of signalling molecules. Furthermore, we show that the promoter was active in the nodule primordia. Together, our data show that plays a vital role in the induction of meristematic activity in root cortical cells and in the establishment of nodule primordia during symbiosis.