Neodiversification of homeologous CLAVATA1-like receptor kinase genes in soybean leads to distinct developmental outcomes

Saeid Mirzaei,Tarik El-Mellouki,Peter M Gresshoff,Shiming Liu,Brett J Ferguson,Khalid Meksem,Jacqueline Batley

doi:10.1038/s41598-017-08252-y

Abstract

The CLAVATA pathway that regulates stem cell numbers of the shoot apical meristem has exclusively been studied in Arabidopsis; as such insight into other species is warranted. In this study, a GmCLV1A mutant (F-S562L) with altered lateral organ development, and two mutants of GmNARK, isolated from a Forrest M2 population (EMS-mutated soybean) were studied. GmCLV1A and GmNARK encode for LRR receptor kinases, and share 92% of protein sequence. While GmNARK is critical for systemic regulation of nodulation (new organ made on the root through symbiosis), we show that GmCLV1A functions locally and has no apparent function in nodulation or root development. However, a recessive, loss-of-function mutation (S562L) in a putative S-glycosylation site of GmCLV1A causes stem nodal identity alterations as well as flower and pod abnormalities (deformed flower and pod). The mutant also exhibits a homeotic phenotype, displaying abnormal leaf development/number, vein-derived leaf emergence, and a thick, faciated stem. The mutant phenotype is also temperature-sensitive. Interestingly, a novel truncated version of GmCLV1A was identified upstream of GmCLV1A that is absent from GmNARK, but is present upstream of the GmNARK orthologues, MtSUNN and PvNARK. Taken together, our findings indicate that GmCLV1A acts on shoot architecture, whereas GmNARK, functions in controlling nodule numbers.

Highlights

Legumes are an important family of angiosperms as they are able to form a symbiosis with bacteria, named rhizobia that fix atmospheric nitrogen gas[1]
Two genes called GmCLV1A and GmNARK (Glycine max Nodule Autoregulation Receptor Kinase; formerly known as GmCLV1B), that belong to the LRR receptor kinase protein family, are highly similar to AtCLV1
Dot plot analysis failed to reveal any significant similarity between the intron sequences of GmCLV1A, GmNARK and AtCLV1A (SM, BJF and PMG, unpublished)

Summary

Introduction

Legumes are an important family of angiosperms as they are able to form a symbiosis with bacteria, named rhizobia that fix atmospheric nitrogen gas[1]. The shoot apical meristem (SAM) of plants contains a population of undifferentiated stem cells, which give rise to aerial organs[4,5,6,7]. This process is best characterised by the CLAVATA (CLV) signalling network in Arabidopsis, where receptors CLV1, CLV2, Coryne and RPK2 (Receptor Protein Kinase 2) interact with the peptide ligand CLV3 to regulate the stem cell reservoir[4, 8,9,10] through WUSCHEL (a homeodomain transcription factor; WUS) gene[11]. At the amino acid level, GmCLV1A and GmNARK are 92% similar to one another[27, 28], and 60% similar to AtCLV1

Methods

Results

Conclusion