A Ubiquitin Ligase of Symbiosis Receptor Kinase Involved in Nodule Organogenesis      

Abstract

The symbiosis receptor kinase (SymRK) is required for morphological changes of legume root hairs triggered by rhizobial infection. How protein turnover of SymRK is regulated and how the nodulation factor signals are transduced downstream of SymRK are not known. In this report, a SymRK-interacting E3 ubiquitin ligase (SIE3) was shown to bind and ubiquitinate SymRK. The SIE3-SymRK interaction and the ubiquitination of SymRK were shown to occur in vitro and in planta. SIE3 represents a new class of plant-specific E3 ligases that contain a unique pattern of the conserved CTLH (for C-terminal to LisH), CRA (for CT11-RanBPM), and RING (for Really Interesting New Gene) domains. Expression of SIE3 was detected in all tested tissues of Lotus japonicus plants, and its transcript level in roots was enhanced by rhizobial infection. The SIE3 protein was localized to multiple subcellular locations including the nuclei and plasma membrane, where the SIE3-SymRK interaction took place. Overexpression of SIE3 promoted nodulation in transgenic hairy roots, whereas downregulation of SIE3 transcripts by RNA interference inhibited infection thread development and nodule organogenesis. These results suggest that SIE3 represents a new class of E3 ubiquitin ligase, acts as a regulator of SymRK, and is involved in rhizobial infection and nodulation in L. japonicus.

Structure of the Arabidopsis TOPLESS corepressor provides insight into the evolution of transcriptional repression

“…This motif was first identified in RanBP9 (human Ran binding protein 9) for mediating the interaction with FMRP (fragile X mental retardation protein) in the microtubule organizing center (35). CRA motifs are present in thousands of eukaryotic proteins such as RanBPM in human or E3 ligases proteins (SIE3 in plants or Gid in yeast) (35)(36)(37). They are often associated with the CTLH domain, but with variable-length spacers between them.…”

A Laser Dissection-RNAseq Analysis Highlights the Activation of Cytokinin Pathways by Nod Factors in the Medicago truncatula Root Epidermis

“…The ubiquitin proteasome machinery comprises many genes involved in the regulation of signaling/ developmental processes, including response to phytohormones and positive or negative roles for rhizobium infection and nodule development (Vinardell et al, 2003;Shimomura et al, 2006;Kiss et al, 2009;Mbengue et al, 2010;Den Herder et al, 2012;Yuan et al, 2012). Nineteen putative ubiquitin proteasome genes were scored as NF up-regulated, among which two genes encoding, respectively, a close homolog of LUMPY INFECTIONS (MtLIN), primarily required for infection thread growth in RH (Kiss et al, 2009), and a nodulation-specific SEVEN-IN-ABSENTIA (SINA) domain protein, very distantly related to LjSINA4, involved in SYMRK turnover (Den Herder et al, 2012; Table III; Supplemental Table S3).…”

GmEXPB2, a Cell Wall β-Expansin Gene, Affects Soybean Nodulation through Modifying Root Architecture and Promoting Nodule Formation and Development

“…A number of genes from many legumes contribute to positive regulation of nodule numbers. Examples include symbiosis receptor kinase-interacting E3 Ubiquitin ligase from L. japonicus (Yuan et al, 2012) and MtSymSCL1 (a SCARECROW-like gene) from M. truncatula (Kim and Nam, 2013). On the other hand, legumes have developed a systemic negative feedback regulatory pathway, known as autoregulation of nodulation, to control nodule numbers by long-distance signaling (Oka-Kira and Kawaguchi, 2006;Magori and Kawaguchi, 2009;Reid et al, 2011).…”