Distinct GmASMTs are involved in regulating transcription factors and signalling cross-talk across embryo development, biotic, and abiotic stress in soybean.

N-Acetylserotonin O-methyltransferase (ASMT) is the final enzyme involved
in melatonin biosynthesis. Identifying the expression of ASMT will reveal
the regulatory role in the development and stress conditions in soybean.
To identify and characterize ASMT in soybean (GmASMT), we employed
genome-wide analysis, gene structure, cis-acting elements, gene expression,
co-expression network analysis, and enzyme assay. We found seven pairs of
segmental and tandem duplication pairs among the 44 identified GmASMTs
by genome-wide analysis. Notably, co-expression network analysis reported
that distinct GmASMTs are involved in various stress response. For example,
GmASMT3, GmASMT44, GmASMT17, and GmASMT7 are involved in embryo
development, heat, drought, aphid, and soybean cyst nematode infections,
respectively. These distinct networks of GmASMTs were associated with
transcription factors (NAC, MYB, WRKY, and ERF), stress signalling, isoflavone
and secondary metabolites, calcium, and calmodulin proteins involved in
stress regulation. Further, GmASMTs demonstrated auxin-like activities by
regulating the genes involved in auxin transporter (WAT1 and NRT1/PTR) and
auxin-responsive protein during developmental and biotic stress. The current
study identified the key regulatory role of GmASMTs during development and
stress. Hence GmASMT could be the primary target in genetic engineering for
crop improvement under changing environmental conditions.