Transcriptome Profiling of the Shoot and Root Tips of S562L, a Soybean GmCLAVATA1A Mutant

Abstract

Plant shoot apical meristems (SAM) and root apical meristems (RAM) contain stem cells that form overall-plant architecture. Mechanisms acting in these regions keep a balance between the stem cell population and differentiation. These mechanisms are well-studied in Arabidopsis, but little is known in the legume soybean (Glycine max (L.) Merr.). In Arabidopsis, the Leucine-rich repeat (LRR) Receptor kinase CLAVATA1 (CLV1) is a crucial regulator of this process in the SAM. In soybean, the receptor most similar to ATCLV1 is GmNARK, which is involved in nodulation control. In contrast, the homeologous partner of GmNARK in soybean, called GmCLV1A, appears to have no function in ‘Autoregulation of nodulation’ (AON) a role in regulating shoot architecture in the SAM. Here, the transcriptome of the shoot and root tip areas of a chemically induced and TILLING-selected GmCLV1A missense mutant, S562L, and its wild type, cultivar Forrest, were analysed to identify genes which are affected by impaired function of GmCLV1A. Among the differentially expressed genes identified, many were categorised as having a role in receptor kinase activity, transcription or defense/stress-response. Molecular categories over-represented in the shoot tip of the mutant include those involved in hormone biosynthesis/activity and secondary metabolism, signalling, photosynthesis, and transport. Functional categories including those involved in polyamine metabolism, nucleotide metabolism, RNA regulation, protein targeting and protein degradation were under-represented in the shoot tip of the mutant. In the root tip, categories associated with signal ling, transport, protein synthesis and metabolism were over-represented in the mutant, while categories associated with cell wall degradation, stress, RNA regulation, protein degradation and targeting were under-represented in the mutant. Factors similar to Arabidopsis regulatory components are most likely functioning in specialised shoot structures in legumes. Furthermore, GmCLV1A may have an unexpected role in the regulation of flavonoid biosynthesis in soybean.