Activation of secondary cell wall biosynthesis by miR319‐targeted TCP4 transcription factor

Abstract

SummaryThe overexpression of miR319 in plants results in delayed senescence, and high levels of miR319‐targeted TCP4 transcription factor cause premature onset of this process. However, the underlying mechanisms of this pathway remain elusive. Here, we found that miR319 overexpression results in a decrease in TCP4 abundance and secondary cell wall formation in the stem. Conversely, constitutive expression of miR319‐resistant TCP4 promotes secondary cell wall formation, indicating that miR319‐mediated TCP4 controls secondary cell wall formation during development. Further analysis revealed that TCP4 might directly bind the promoter of VND7 to activate its expression, which triggers the expression of a VND7 transcriptional network associated with secondary cell wall biosynthesis and programmed cell death and accelerates vessel formation. In addition, the development process gradually increased TCP4 expression. These results suggest that miR319 and its target TCP4 can act as switches that turn on secondary cell wall synthesis and programmed cell death.

Heteroexpression of Osa-miR319b improved switchgrass biomass yield and feedstock quality by repression of PvPCF5

“…Our data clearly showed that miR319-PvPCF5 pathway negatively regulated stem lignin content. Similar results were also reported in Arabidopsis [33]. However, we did not find differences in flowering time between WT and transgenic plants.…”

“…In this study, PvPCF7 and PvPCF8 showed higher expression level in developed stems, and were negatively correlated with miR319 expression. Similarly, AtTCP4, a positive lignin content regulator, showed a similar expression pattern during Arabidopsis development [33]. However, the miR319 target PvPCF5/6/21 showed the opposite expression pattern with PvPCF7/8 during stem development.…”

“…NAC-MYB-based transcriptional regulatory system regulates secondary cell wall biosynthesis and has been well studied in switchgrass [11,13,47,48]. In Arabidopsis, miR319 target gene TCP4 could directly activate expression of NAC TF AtVND7 (one master regulator in cell wall biosynthesis), which resulted in increases in lignin and cellulose content [33]. However, no TCP binding site was predicted in the promoter of homolog gene PvVND7 using JASPAR software (Additional file 6: Table S3).…”

“…BR and JA, two plant growth regulatory hormones, were reported highly correlated to plant biomass yield and lignin content [31,32]. Furthermore, AtTCP4 directly activated VASCU-LAR-related NAC-DOMAIN7 (VND7), a NAC subgroup gene, enhancing lignin and cellulose content and accelerating vessel formation [33]. In addition, overexpression of miR319 in switchgrass enhanced ethylene production and expression of down-stream genes of ethylene signaling transduction, such as upregulated expression of some ERFs [34].…”

CIN‐TCP transcription factors: Transiting cell proliferation in plants

“…CIN‐TCPs also regulate differentiation of vasculature in the leaf. TCP4 directly activates VASCULAR‐RELATED NAC‐DOMAIN7 ( VND7 ) expression, leading to the differentiation of xylem vessel elements . VND7 belongs to the NAM/ATAF/CUC family of transcription factors and controls several downstream factors required for switching on genes involved in cellulose and lignin biosynthesis for secondary cell wall deposition critical for xylem differentiation and vessel formation .…”