Genome-Wide Identification and Analysis of the Growth-Regulating Factor Family in Zanthoxylum armatum DC and Functional Analysis of ZaGRF6 in Leaf Size and Longevity Regulation

Abstract

Growth-regulating factors (GRFs) are plant-specific transcription factors that play an important role in plant growth and development. In this study, fifteen <i>GRF</i> gene members containing QLQ and WRC domains were identified in <i>Zanthoxylum armatum</i>. Phylogenetic and collinearity analysis showed that ZaGRFs were closely related to CsGRFs and AtGRFs, and distantly related to OsGRFs. There are a large number of cis-acting elements related to hormone response and stress induction in the <i>GRF</i> gene promoter region of <i>Z. armatum</i>. Tissue-specific expression analysis showed that except for <i>ZaGRF7</i>, all the <i>ZaGRFs</i> were highly expressed in young parts with active growth and development, including terminal buds, seeds, and young flowers, suggesting their key roles in <i>Z. armatum</i> growth and development. Eight <i>ZaGRFs</i> were selected to investigate the transcriptional response to auxin, gibberellin and drought treatments. A total of six <i>ZaGRFs</i> in the NAA treatment, four <i>ZaGRFs</i> in the GA₃ treatment, and six <i>ZaGRFs</i> in the PEG treatment were induced and significantly up-regulated. Overexpression of <i>ZaGRF6</i> increased branching and chlorophyll content and delayed senescence of transgenic <i>Nicotiana benthamiana</i>. <i>ZaGRF6</i> increased the expression of <i>CRF2</i> and suppressed the expression of <i>ARR4</i> and <i>CKX1</i>, indicating that <i>ZaGRF6</i> is involved in cytokinin metabolism and signal transduction. These research results lay a foundation for further analysis of the <i>GRF</i> gene function of <i>Z. armatum</i> and provide candidate genes for growth, development, and stress resistance breeding of <i>Z. armatum</i>.