The Populus Class III HD ZIP Transcription Factor POPCORONA Affects Cell Differentiation during Secondary Growth of Woody Stems

Abstract

The developmental mechanisms regulating cell differentiation and patterning during the secondary growth of woody tissues are poorly understood. Class III HD ZIP transcription factors are evolutionarily ancient and play fundamental roles in various aspects of plant development. Here we investigate the role of a Class III HD ZIP transcription factor, POPCORONA, during secondary growth of woody stems. Transgenic Populus (poplar) trees expressing either a miRNA-resistant POPCORONA or a synthetic miRNA targeting POPCORONA were used to infer function of POPCORONA during secondary growth. Whole plant, histological, and gene expression changes were compared for transgenic and wild-type control plants. Synthetic miRNA knock down of POPCORONA results in abnormal lignification in cells of the pith, while overexpression of a miRNA-resistant POPCORONA results in delayed lignification of xylem and phloem fibers during secondary growth. POPCORONA misexpression also results in coordinated changes in expression of genes within a previously described transcriptional network regulating cell differentiation and cell wall biosynthesis, and hormone-related genes associated with fiber differentiation. POPCORONA illustrates another function of Class III HD ZIPs: regulating cell differentiation during secondary growth.

Functional plasticity of miR165/166 in plant development revealed by small tandem target mimic

“…Zhou et al also predicted that vascular defects induced by miR165 overexpression is linked with an alteration of positional signal, likely mediated by auxin [33]. More recently, a Populus CORONA/ATHB15 was also reported to be involved in hormone-related gene expression [36].…”

Transcriptomic analysis of juvenile wood formation during the growing season in Pinus canariensis

“…Consistently, Du et al (2011) and Ong and Wickneswari (2012) reported this gene as being a negative regulator of xylem development in poplar and acacia, respectively. In a similar way, among the WOX family, a WOX8-like gene was detected in cluster 2.…”

“…as a negative regulator of vascular tissue development under the control of miRNA165/166 (Ong and Wickneswari 2012). On the contrary, an miRNAresistant POPCORONA has been suggested to be involved in the upregulation of cellulose biosynthesis-related genes, but also with the down-regulation of lignin deposition-related genes in poplar (Du et al 2011).…”

Forest tree genomics: 10 achievements from the past 10 years and future prospects

“…Furthermore, transgenic poplar trees expressing either a miRNA-resistant P O P C O R O N A o r a s y n t h e t i c m i R N A t a rg e t i n g POPCORONA have been used to infer the function of POPCORONA during secondary growth: the synthetic miRNA-mediated knockdown of POPCORONA expression resulted in abnormal lignification in pith cells, whereas the overexpression of a miRNA-resistant POPCORONA delayed the lignification of xylem and phloem fibers during secondary growth. The misexpression of POPCORONA was also shown to result in a coordinated change in gene expression within a previously described transcriptional network regulating cell differentiation and cell wall biosynthesis and in the expression of hormone-related genes associated with fiber differentiation (Du et al 2011).…”