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

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 signalling, transport, protein synthesis and metabolism were overrepresented
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.