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

Abstract

BYPASS1 (BPS1), which is a well-conserved gene in plants, is required for normal root and shoot development. In the absence of BPS1 gene function, Arabidopsis overproduces a mobile signalling compound (the BPS1 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 Rhizobium symbiosis. We explored the role of Phaseolus vulgaris BPS1 during nodule primordium development using an RNA-interference (RNAi) silencing approach. Our results show that upon Rhizobium infection, the PvBPS1-RNAi 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 PvBPS1-RNAi root nodule phenotype was partially rescued by exogenous application of fluridone, a carotenoid biosynthesis inhibitor, which was used because the carotenoids are precursors of BPS1 signalling molecules. Furthermore, we show that the PvBPS1 promoter was active in the nodule primordia. Together, our data show that PvBPS1 plays a vital role in the induction of meristematic activity in root cortical cells and in the establishment of nodule primordia during Phaseolus-Rhizobium symbiosis.

Celebrating 20 Years of Genetic Discoveries in Legume Nodulation and Symbiotic Nitrogen Fixation

“…RNAi silencing of GmBCH1/2 impaired nodule development and SNF (Kim et al, 2013). Silencing of P. vulgaris BYPASS1 (PvBPS1) resulted in defective nodule development, which was partially rescued by the carotenoid biosynthesis inhibitor fluridone (Arthikala et al, 2018).…”

Back From the Dead: The Atypical Kinase Activity of a Pseudokinase Regulator of Cation Fluxes During Inducible Immunity

“…We identified 32 and 18 phosphorylated peptides using either Mn 2+ or Mg 2+ as cofactors, respectively ( Figure 1 , Supplementary Tables 2 , 3 , and Supplementary Data 1 ). Four peptides were phosphorylated in both conditions, including one derived from a pectin methylesterase involved in cell wall-mediated defense (PME39, AT4G02300), the BYPASS1 protein which is required for root responses to Rhizobium infection, an ankyrin repeat protein (AT3G04470) and an RNA helicase family protein (AT1G08050) that is oxidized following flg22 or salicylic acid treatments ( Bethke et al, 2009 ; Liu et al, 2015 ; Arthikala et al, 2018 ). The majority of the ILK1 peptide targets were localized to the nucleus or plasma membrane, consistent with previous observations that ILK1 can be found in the plasma membrane, the endoplasmic reticulum, and the nucleus ( Brauer et al, 2016 ; Supplementary Figure 1A and Supplementary Data 1 ).…”

Back from the dead: the atypical kinase activity of a pseudokinase regulator of cation fluxes during inducible immunity

“…We identified 32 and 18 phosphorylated peptides using either Mn 2+ or Mg 2+ as cofactors, respectively (Figure 1, Supplementary Tables 2, 3, Supplemental Data 1). Four peptides were phosphorylated in both conditions, including one derived from a pectin methylesterase involved in cell wall-mediated defense (PME39, AT4G02300), the BYPASS1 protein which is required for root responses to Rhizobium infection, an ankyrin repeat protein (AT3G04470) and an RNA helicase family protein (AT1G08050) that is oxidized following flg22 or salicylic acid treatments (Bethke et al, 2009; Liu et al, 2015; Arthikala et al, 2018). The majority of the ILK1 peptide targets were localized to the nucleus or plasma membrane, consistent with previous observations that ILK1 can be found in the plasma membrane, the endoplasmic reticulum, and the nucleus (Brauer et al, 2016)(Supplementary Figure 1A, Supplemental Data 1).…”