Genome-wide identification and functional characterization of LBD transcription factors uncover their stress adaptation mechanisms in tobacco and eggplant

Abstract

The Lateral Organ Boundaries Domain protein family comprises a group of plant-specific transcription factors involved in diverse developmental and stress-response processes. We identified 106 NtLBD genes in tobacco (Nicotiana tabacum L.) and 50 SmLBD genes in eggplant (Solanum melongena L.), and classified them into Classes I and II. Duplication analysis identified 26 segmental and 3 tandem duplicated gene pairs, while interspecies synteny analysis revealed 17 tobacco–Arabidopsis thaliana and 31 eggplant–Arabidopsis thaliana syntenic pairs. Expression profiling showed broad tissue expression, with relatively high transcript abundance in roots and stems, and selected LBD proteins were localized to the nucleus. VIGS constructs targeting NtLBD4/NtLBD31 in tobacco and SmLBD19/SmLBD48 in eggplant were used for preliminary functional assessment. In tobacco, these treatments were associated with reduced expression of ABA-responsive genes, less visible injury under low-temperature stress, and increased susceptibility to bacterial wilt. In eggplant, they were associated with increased expression of ABA biosynthesis and signaling related genes, reduced visible cold injury, and enhanced bacterial wilt resistance. Expression changes in related LBD members further suggested possible functional redundancy or compensatory regulation. These findings indicate that selected LBD genes and their associated regulatory networks participate in ABA responses, low-temperature adaptation, and pathogen defense in tobacco and eggplant, and they further underscore the potential utility of these genes as targets for improving stress tolerance in Solanaceous species, although additional experimental confirmation is warranted.