Genome-Wide Survey of the Potential Function of CrLBDs in Catharanthus roseus MIA Biosynthesis

<i>Catharanthus roseus</i> (<i>C</i>. <i>roseus</i>) can produce over 150 types of monoterpenoid indole alkaloids (MIAs), including vinblastine and vincristine, which are currently the primary sources of these alkaloids. Exploring the complex regulatory mechanisms of <i>C</i>. <i>roseus</i> is significant for resolving MIA biosynthesis. The Lateral Organ Boundaries Domain (LBD) is a plant-specific transcription factor family that plays crucial roles in the physiological processes of plant growth, stress tolerance, and specialized metabolism. However, the LBD gene family has not been extensively characterized in <i>C</i>. <i>roseus</i>, and whether its members are involved in MIA biosynthesis is still being determined. A total of 34 <i>C</i>. <i>roseus LBD</i> (<i>CrLBD</i>) genes were identified. RNA-Seq data were investigated to examine the expression patterns of <i>CrLBD</i> genes in various tissues and methyl jasmonate (MeJA) treatments. The results revealed that the Class Ia member <i>CrLBD4</i> is positively correlated with iridoid biosynthetic genes (<i>p</i> < 0.05, r ≥ 0.8); the Class IIb member CrLBD11 is negatively correlated with iridoid biosynthetic genes (<i>p</i> < 0.05, r ≤ -0.8). Further validation in leaves at different growth stages of <i>C. roseus</i> showed that <i>CrLBD4</i> and <i>CrLBD11</i> exhibited different potential expression trends with iridoid biosynthetic genes and the accumulation of vindoline and catharanthine. Yeast one-hybrid (Y1H) and subcellular localization assays demonstrated that CrLBD4 and CrLBD11 could bind to the "aattatTCCGGccgc" <i>cis</i>-element and localize to the nucleus. These findings suggest that CrLBD4 and CrLBD11 may be potential candidates for regulating MIA biosynthesis in <i>C. roseus</i>. In this study, we systematically analyzed the CrLBD gene family and provided insights into the roles of certain CrLBDs in the MIA biosynthesis of <i>C. roseus</i>.