The Regulation of Xylem Development by Transcription Factors and Their Upstream MicroRNAs.

Xylem, as a unique organizational structure of vascular plants, bears water transport and supports functions necessary for plant survival. Notably, secondary xylem in the stem (i.e., wood) also has important economic and ecological value. In view of this, the regulation of xylem development has been widely concerned. In recent years, studies on model plants and poplar have shown that transcription factors play important regulatory roles in various processes of xylem development, including the directional differentiation of procambium and cambium into xylem, xylem arrangement patterns, secondary cell wall formation and programmed cell death. This review focuses on the regulatory roles of widely and thoroughly studied , and transcription factor gene families in xylem development, and it also pays attention to the regulation of their upstream microRNAs. In addition, the existing questions in the research and future research directions are prospected.