Knockdown of miR393 Promotes the Growth and Biomass Production in Poplar

Abstract

Short tandem target mimic (STTM), which is composed of two short sequences mimicking small RNA target sites, separated by a linker of optimal size, can block the functions of all members in a miRNA family. microRNA393 (miR393), which is one of the conserved miRNA families in plants, can regulate plant root growth, leaf development, plant architecture, and stress resistance. In order to verify the role of miR393 in the secondary growth of trees, we created its STTM transgenic poplar lines (STTM393). The expression of miR393 in STTM393 lines was reduced by over 10 times compared with the control plants. STTM393 lines showed promoted growth with about 20% higher, 15% thicker, and 2–4 more internodes than the control plants after 3 months of growth. The cross-section of the stems showed that STTM393 lines had wider phloem, xylem, and more cambium cell layers than control plants, and the lignin content in STTM393 lines was also higher as revealed by staining and chemical determination. Based on the transcriptome analysis, the genes related to the auxin signaling pathway, cell cyclin, cell expansion, and lignin synthesis had higher expression in STTM393 lines than that in control plants. The higher expression levels of FBL family members suggested that the auxin signaling pathway was strengthened in STTM393 lines to promote plant growth. Therefore, the knockdown of miR393 using the STTM approach provides a way to improve poplar growth and biomass production.

The Intersection of Non-Coding RNAs Contributes to Forest Trees’ Response to Abiotic Stress

“…Related work has also been carried out successfully in forest trees such as Populus . For example, knockdown of miR393 promoted growth and biomass production in poplar, which was verified in STTM393 transgenic poplar lines [ 88 ]. RNAi suppression of DNA methylation affected the drought stress response and genome integrity in transgenic poplar [ 89 ].…”

Lignin engineering in forest trees: From gene discovery to field trials

“…(2022) P. alba × P. grandidentata CPL overexpression ↓5% ↓S/G, increased p -hydroxybenzoates ↑ n.d. ↓ Mottiar et al. (2022) P. alba × P. glandulosa miR393 suppression via STTM slightly ↑ n.d. n.d. n.d. ↑ Chu et al. (2021) P. tremula × Populus tremuloides HpSK overexpression WT ↑S/G, increased H units ↑ n.d. ↓ Hu et al.…”

“…Transcript levels can be post-transcriptionally regulated via microRNAs. MicroRNA393 (miR393) is a conserved miRNA family in plants that can regulate root growth, plant architecture, leaf development, and stress resistance ( Chu et al., 2021 ). Poplar lines in which the miR393 family was blocked via short tandem target mimic (STTM) show an increased growth compared with WT trees, as well as a higher expression of lignin biosynthetic genes and a higher stem lignin content.…”

“…Poplar lines in which the miR393 family was blocked via short tandem target mimic (STTM) show an increased growth compared with WT trees, as well as a higher expression of lignin biosynthetic genes and a higher stem lignin content. How miR393 regulates lignin biosynthetic genes remains unknown ( Chu et al., 2021 ). Overexpression of another microRNA, miR828, in poplar results in a reduced lignin content (−13%) in wood and a decreased biomass yield ( Wang et al., 2022 ).…”

The miR393-Target Module Regulates Plant Development and Responses to Biotic and Abiotic Stresses

“…Based on sRNA-seq and degradome analysis, Zhao et al (2016) speculated that miR393 and the target genes might be involved in the internode elongation and development under maize ears [ 40 ]. The inhibition of miR393 in poplar was shown to promote phloem and xylem growth and increase lignin content through increasing the gene expression in the auxin signaling pathway, and the short tandem target mimic lines of miR393 (STTM393) showed more internodes and promoted growth compared with the control [ 57 ].…”