RESUMO
Liriodendron tulipifera L. is an ornamental tree species with extraordinarily lobed leaves. However, the mechanisms underlying lobed leaf formation in plants remain unclear. The transcription factor, ARABIDOPSIS THALIANA HOMEBOX 6 (HB6), plays a role in regulating leaf margin development. HB6 is involved in cell division and differentiation of developmental organs and negatively regulates abscisic acid (ABA) signal transmission under external abiotic stress; it is unclear whether HB6 performs a pivotal role in leaf morphogenesis in L. tulipifera. In this study, full-length LtuHB6 from L. tulipifera was heterologously expressed in tobacco and Arabidopsis thaliana; its expression pattern was analyzed to determine its potential role in leaf development. In addition, LtuHB6 is localized in the nucleus and cell membrane of tobacco leaves. The expression of LtuHB6 was highest in mature leaves compared to the other stages of leaf development (bud growth, young leaves, and leaf senescence). Transgenic A. thaliana plants overexpressing LtuHB6 exhibited an abnormal phenotype with lobed leaves. Moreover, LtuHB6 overexpression significantly affected the expression of seven genes related to leaf serration in the initial stage of leaf primordia and altered the expression levels of hormonal genes. Our findings indicate that LtuHB6 is an essential regulatory factor in L. tulipifera lobed-leaf formation and is involved in regulating and responding to hormones. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01254-9.
RESUMO
BACKGROUND: Liriodendron chinense is a distinctive ornamental tree species due to its unique leaves and tulip-like flowers. The discovery of genes involved in leaf development and morphogenesis is critical for uncovering the underlying genetic basis of these traits. Genes in the AP2/ERF family are recognized as plant-specific transcription factors that contribute to plant growth, hormone-induced development, ethylene response factors, and stress responses. RESULTS: In this study, we identified 104 putative AP2/ERF genes in the recently released L. chinense genome and transcriptome database. In addition, all 104 genes were grouped into four subfamilies, the AP2, ERF, RAV, and Soloist subfamilies. This classification was further supported by the results of gene structure and conserved motif analyses. Intriguingly, after application of a series test of cluster analysis, three AP2 genes, LcERF 94, LcERF 96, and LcERF 98, were identified as tissue-specific in buds based on the expression profiles of various tissues. These results were further validated via RT-qPCR assays and were highly consistent with the STC analysis. We further investigated the dynamic changes of immature leaves by dissecting fresh shoots into seven discontinuous periods, which were empirically identified as shoot apical meristem (SAM), leaf primordia and tender leaf developmental stages according to the anatomic structure. Subsequently, these three candidates were highly expressed in SAM and leaf primordia but rarely in tender leaves, indicating that they were mainly involved in early leaf development and morphogenesis. Moreover, these three genes displayed nuclear subcellular localizations through the transient transformation of tobacco epidermal cells. CONCLUSIONS: Overall, we identified 104 AP2/ERF family members at the genome-wide level and discerned three candidate genes that might participate in the development and morphogenesis of the leaf primordium in L. chinense.