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Updated: Sep 16, 2025

The Use of Induced Somatic Sector Analysis ISSA for Studying Genes and Promoters Involved in Wood Formation and Secondary Stem Development
Published on: October 5, 2016
Phytochrome-interacting factor3 (PIF3) orthologs orchestrate stem elongation and wood formation in Populus
Xingyue Xiao1, Hongli Cheng1, Jianghai Mo1
1Chongqing Key Laboratory of Tree Germplasm Innovation and Utilization, Integrative Science Center of Germplasm Creation, Key Laboratory of Eco-environments of Three Gorges Reservoir Region, Ministry of Education, School of Life Sciences, Southwest University, Chongqing 400715, China.
Abstract:
Phytochrome-interacting factors (PIFs) have been established as negative regulators of vascular patterning and xylem differentiation in the herbaceous plant Arabidopsis thaliana, however, the regulatory role of PIFs in secondary growth in woody species remains unclear. Here, we examines the expression patterns and involvement of PtoPIF3.1 and PtoPIF3.2 during stem growth and secondary xylem development in Populus tomentosa. Overexpression of either PtoPIF3.1 or PtoPIF3.2 significantly enhances both longitudinal stem growth and radial wood development. Conversely, Ptopif3.1 and Ptopif3.2 mutants generated by CRISPR-mediated genome editing exhibit reciprocal phenotypic defects. Exogenous auxin application partially restores the phenotypes of Ptopif3.1 and Ptopif3.2 mutants, and the auxin biosynthesis-deficient mutant Ptoyuc8 exhibits developmental abnormalities similar to those observed in Ptopif3 mutants. Further analysis reveal that PtoPIF3s directly bind to and activate expression of PtoYUC8 and cell expansion-related genes PtoEXPA1.1/1.2, while modulating cambial division and expression of secondary xylem development marker genes (PtoWOX4, PtoANT, PtoCYCD3s, and PtoHB7/8) through auxin-mediated signaling. Together, our findings establish PtoPIF3.1/3.2 as key regulators that coordinate stem elongation and secondary growth in Populus, highlighting the functional divergence of PIF homologs between herbaceous and woody species.
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