Genome-wide identification and functional characterization of the LBD transcription factor gene family in Zanthoxylum armatum DC. reveal its potential role in leaf variation.

BACKGROUND

Leaf morphology plays a crucial role in forecasting the productivity and environmental adaptability of economically important trees. Plants with larger leaves usually have higher photosynthesis efficiency and can accumulate more nutrients, thereby increasing yield. In the natural population of Z. armatum, due to long-term selection, the leaves size and shape show rich diversity in different latitude regions. This diversity is the result of plants' adaptation to different environments. However, to date, no studies have systematically revealed the genetic mechanism of Z. armatum leaf variation. In higher plants, lateral organ boundaries domain (LBD) proteins comprise a unique family of transcription factors that play pivotal roles in the establishment of plant leaf polarity and morphogenesis. However, little is currently known regarding the LBD gene family in Z. armatum.

RESULTS

In this study, we identified 97 members of the LBD gene family within the genome of Z. armatum, which were unevenly distributed among the 33 chromosomes of this species. Physicochemical analysis revealed that these ZaLBDs are hydrophilic proteins with nuclear subcellular localization, whereas phylogenetic analysis of 234 LBD protein from different species indicated that these can be divided into five subfamilies (Ia, Ib, Ic, Id, and II). Furthermore, and analysis of cis-acting regulatory elements revealed that ZaLBDs may play important roles in responses to abiotic stress, hormone signal transduction, and plant growth and development. Transcriptomic data were used to compare the expression of these genes in leaves with differing morphologies collected from Z. armatum plants originating from sites at three different latitudes within the distribution range of this species. These data revealed differences in the expression of 14 genes among Z. armatum populations with different latitudinal distributions, with difference in the expression of the ZaLBD45 gene being the most pronounced, the expression trend of ZaLBD19 was consistent with the trend of leaf size. Moreover, qRT-PCR analysis verified that the relative expression of these genes was highly consistent with the transcriptomic data.

CONCLUSIONS

In this study, we comprehensively analyzed the functional characteristics and expression patterns of genes in the LBD family within the heterophyllous plant Z. armatum distributed at different latitudes. By mediating the regulation of leaf morphology, these genes may play important roles in the response to abiotic stress and adaptation to ecological changes. Our findings will not only enhance our understanding of the genetic mechanisms underlying the adaptive variation in Z. armatum but also provide valuable resources for the genetic improvement of this plant.