Characterization of the Liriodendron Chinense MYB Gene Family and Its Role in Abiotic Stress Response

Abstract

<i>Liriodendron chinense</i> (<i>Lchi</i>) is a Magnoliaceae plant, which is a basic angiosperm left behind by the Pleistocene and mainly distributed in the south of the Yangtze River. <i>Liriodendron hybrids</i> has good wood properties and is widely used in furniture and in other fields. It is not clear if they can adapt to different environmental conditions, such as drought and high and low temperatures, and the molecular mechanisms for this adaptation are unknown. Among plant transcription factors (TFs), the <i>MYB</i> gene family is one of the largest and is often involved in stress or adversity response signaling, growth, and development. Therefore, studying the role of MYBTFs in regulating abiotic stress signaling, growth, and development in <i>Lchi</i> is helpful to promote afforestation in different environments. In our research, a genome-wide analysis of the <i>LchiMYB</i> gene family was performed, including the phylogenetic relationship tree, gene exon-intron structure, collinearity, and chromosomal position. According to the evolutionary tree, 190 <i>LchiMYBs</i> were divided into three main branches. <i>LchiMYBs</i> were evenly distributed across 19 chromosomes, with their collinearity, suggesting that segment duplication events may have contributed to <i>LchiMYB</i> gene expansion. Transcriptomes from eight tissues, 11 stages of somatic embryogenesis, and leaves after cold, heat, and drought stress were used to analyze the function of the <i>MYB</i> gene family. The results of tissue expression analysis showed that most <i>LchiMYB</i> genes regulated bark, leaf, bud, sepal, stigma, and stamen development, as well as the four important stages (ES3, ES4, ES9, and PL) of somatic embryogenesis. More than 60 <i>LchiMYBs</i> responded to heat, cold, and drought stress; some of which underwent gene duplication during evolution. <i>LchiMYB3</i> was highly expressed under all three forms of stress, while <i>LchiMYB121</i> was strongly induced by both cold and heat stress. Eight genes with different expression patterns were selected and verified by quantitative real-time PCR (qRT-PCR) experiments. The results suggested that these <i>LchiMYBs</i> may regulate <i>Lchi</i> growth development and resistance to abiotic stress. This study shows the cross-regulatory function of <i>LchiMYBs</i> in the growth and development, asexual reproduction, and abiotic resistance of <i>Lchi</i>. This information will prove pivotal to directing further studies on the biological function of <i>Lchi</i> MYBTFs in genetic improvement and abiotic stress response.