Overexpression of SbMyb60 in Sorghum bicolor impacts both primary and secondary metabolism

Abstract

SummaryFew transcription factors have been identified in C 4 grasses that either positively or negatively regulate monolignol biosynthesis.Previously, the overexpression of SbMyb60 in sorghum (Sorghum bicolor) has been shown to induce monolignol biosynthesis, which leads to elevated lignin deposition and altered cell wall composition. To determine how SbMyb60 overexpression impacts other metabolic pathways, RNA-Seq and metabolite profiling were performed on stalks and leaves.35S::SbMyb60 was associated with the transcriptional activation of genes involved in aromatic amino acid, S-adenosyl methionine (SAM) and folate biosynthetic pathways. The high coexpression values between SbMyb60 and genes assigned to these pathways indicate that SbMyb60 may directly induce their expression. In addition, 35S::SbMyb60 altered the expression of genes involved in nitrogen (N) assimilation and carbon (C) metabolism, which may redirect C and N towards monolignol biosynthesis. Genes linked to UDP-sugar biosynthesis and cellulose synthesis were also induced, which is consistent with the observed increase in cellulose deposition in the internodes of 35S::SbMyb60 plants. However, SbMyb60 showed low coexpression values with these genes and is not likely to be a direct regulator of cell wall polysaccharide biosynthesis.These findings indicate that SbMyb60 can activate pathways beyond monolignol biosynthesis, including those that synthesize the substrates and cofactors required for lignin biosynthesis.

Transcriptional Regulation of Sorghum Stem Composition: Key Players Identified Through Co-expression Gene Network and Comparative Genomics Analyses

“…SbMYB60 and its paralog SbMYB60b are orthologs of AtMYB58 and AtMYB63. SbMYB60 has been functionally validated for its role in the sorghum lignin pathway (Scully et al, 2016(Scully et al, , 2017 but it did not pass our correlation threshold. SbMYB60b is allocated to the pink module, and its top subnetwork is medium enriched in one GO term related to lignin, three GO terms related to phenylpropanoid and two GO terms related to flavonoid biosynthesis.…”

Metabolite and transcript profiling of Guinea grass (Panicum maximum Jacq) response to elevated [CO2] and temperature

“…ZmCCR1 mutants with a moderate down-regulation of CCR1 activity increased the digestibility of cell walls without severely modifying lignin content (Tamasloukht et al 2011). The overexpression of SbMyb60 transcription factor in Sorghum bicolor was found to directly impact the monolignol biosynthesis with higher abundance of syringyl lignin, cell wall composition, with increases in soluble phenolic and aromatic amino acids (Scully et al 2016, 2018). The observed increase in abundance of sinapic acid, phenylalanine, and α-Tocopherol under the eT treatment, regardless of [CO 2 ], point to an impact of eT on lignin composition, possibly increased S-type concentrations, although that would need to be tested.…”

Strategies for the production of biochemicals in bioenergy crops

“…2) [114]. Finally, in sorghum, overexpression of MYB transcription factor (SbMyb60) that induces monolignol biosynthesis resulted in higher amount of syringaldehyde crosslinked to cell walls [115].…”