Identification of Grape Laccase Genes and Their Potential Role in Secondary Metabolite Synthesis

Laccase, a copper-containing oxidoreductase, has close links with secondary metabolite biosynthesis in plants. Its activity can affect the synthesis and accumulation of secondary metabolites, thereby influencing plant growth, development, and stress resistance. This study aims to identify the grape laccases (<i>VviLAC</i>) gene family members in grape (<i>Vitis vinifera</i> L.) and explore the transcriptional regulatory network in berry development. Here, 115 <i>VviLACs</i> were identified and divided into seven (Type I-VII) classes. These were distributed on 17 chromosomes and out of 47 <i>VviLACs</i> on chromosome 18, 34 (72.34%) were involved in tandem duplication events. <i>VviLAC1</i>, <i>VviLAC2</i>, <i>VviLAC3</i>, and <i>VviLAC62</i> were highly expressed before fruit color development, while <i>VviLAC4</i>, <i>VviLAC12</i>, <i>VviLAC16</i>, <i>VviLAC18</i>, <i>VviLAC20</i>, <i>VviLAC53</i>, <i>VviLAC60</i> and <i>VviLAC105</i> were highly expressed after fruit color transformation. Notably, <i>VviLAC105</i> showed a significant positive correlation with important metabolites including resveratrol, resveratrol dimer, and peonidin-3-glucoside. Analysis of the transcriptional regulatory network predicted that the 12 different transcription factors target <i>VviLAC</i>s genes. Specifically, WRKY and ERF were identified as potential transcriptional regulatory factors for <i>VviLAC105</i>, while Dof and MYB were identified as potential transcriptional regulatory factors for <i>VviLAC51</i>. This study identifies and provides basic information on the grape LAC gene family members and, in combination with transcriptome and metabolome data, predicts the upstream transcriptional regulatory network of <i>VviLAC</i>s.