MiR319a-mediated salt stress response in poplar

Abstract

Maintenance of intracellular ion balance, especially Na⁺ and K⁺, plays an important role in plant responses to salt stress. Vessels in xylem are responsible for long-distance ion transport in vascular plants. Knowledge on the salt stress response in woody plants in limited. In this study, we identified miR319a as an important regulator in respond to salt stress in poplar. miR319a overexpression transgenic poplar showed a salt-tolerant phenotype, and cytological observation showed reduced cambium cell layers, wider xylem, increased number and lumen area of vessels and fibers, and thinner cell wall thickness in the transgenics. The miR319a-MIMIC plants, meanwhile, had opposite phenotypes, with narrower xylem, reduced number and lumen area of vessels and fibers cells, and increased wall thickness. In addition, overexpression of miR319a driven by the vessel-specific promoter significantly improved the salt tolerance compared with the fiber-specific promoter. The expression levels of PagHKT1;2 and PagSKOR1-b, which encoded high-affinity K⁺ and Na⁺ transporters for Na⁺ efflux and K⁺ influx, respectively, were positively correlated with the vessel number and lumen area. These results suggest that miR319 not only promotes ion transport rates by increasing vessel number and lumen area and reducing cell wall thickness, but also regulates the concentrations of Na⁺ and K⁺ in the xylem by up-regulating PagHKT1;2 and PagSKOR1-b. We demonstrate that miR319 may coordinate the response of poplar to salt stress through both mechanisms, enriching our understanding of the synergistic effects of the secondary xylem structure and long-distance ion transport balance in the salt tolerance of poplar.

Acknowledgements

This work was supported by the National Key Research and Development Program of China (2021YFD2200900 to X.Y.), Fundamental Research Funds of SKLTGB (CAF) (TGBFRF202301 to X.Y.). We thank Prof. Dayong Li (Beijing Academy of Agriculture and Forestry Sciences) and Prof. Wanjun Zhang (China Agricultural University) for sharing plasmids pZH01: OsamiR319a-OE and miR319a-MIMIC. We thank Prof. Jinshan Gui (Zhejiang Agriculture and Forestry University) for sharing plasmids pCAMBIA2300:PdXCP1p-35Smini-GUS and pCAMBIA2300:PdDUF579-9p-35Smini-GUS. We thank Shuai Liu and Dandan Yin (State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing) for their technical assistance for ICP-MS and SEM analyses.

Author contributions

Q.L. and X.Y. conceived the project; Y.C., Q.W., and L.Y. performed the experiments; Q.L. and X.Y. analysed the data; Y.C. and X.Y. wrote the manuscript, with edits from all authors.

Data availability

The sequencing data of this study have been deposited in the National Center for Biotechnology Information Sequence Read Archive database under accession number PRJNA1067826.

Conflict of interest statement

The authors declared no competing interests.

Supplementary data

Supplementary data is available at Horticulture Research online.

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