AtMAN6 coordinates cell growth and secondary cell wall formation in xylem development
We observed that the Arabidopsis endo-1,4-mannanase gene AtMAN6 is involved in the formation of cell walls in vascular tissues. In the inflorescence stem, the man6 mutant had smaller vessel cells with thicker secondary cell walls and shorter fiber cells. Elongation growth was reduced in the root, and secondary cell wall deposition in vessel cells occurred early. Overexpression of AtMAN6 resulted in the inverse phenotypes of the man6 mutant. AtMAN6 was discovered on the plasma membrane and was specifically expressed in vessel cells during its early development. The AtMAN6 protein degraded galactoglucomannan to produce oligosaccharides, which caused secondary cell wall deposition in vessel and fiber cells to be delayed. Transcriptome analysis revealed that the expression of genes involved in the secondary cell wall synthesis pathway was changed in both man6 mutant and AtMAN6 overexpression plants. AtMAN6's carboxyl-terminal cysteine repeats motif (CCRM) was found to facilitate homodimerization and is required for its activity. According to the findings, the oligosaccharides produced by AtMAN6 hydrolysis may act as a signal to mediate this coordination between cell expansion and SCW deposition.