Abstract
LATERAL ORGAN BOUNDARIES (LOB) DOMAIN (LBD) constitute a family of plant-specific transcription factors with key roles in the regulation of plant organ development, pollen development, plant regeneration, pathogen response, and anthocyanin and nitrogen metabolisms. However, the role of LBDs in fruit ripening and in grapevine (Vitis vinifera L.) development and stress responses is poorly documented. By performing a model curation of LBDs in the latest genome annotation 50 genes were identified. Phylogenetic analysis showed that LBD genes can be grouped into two classes mapping on 16 out of the 19 V. vinifera chromosomes. New gene subclasses were identified that have not been characterized in other species. Segmental and tandem duplications contributed significantly to the expansion and evolution of the LBD gene family in grapevine as noticed for other species. The analysis of cis-regulatory elements and transcription factor binding sites in the VviLBD promoter regions suggests the involvement of several hormones in the regulation of LBDs expression. Expression profiling suggest the involvement of LBD transcription factors in grapevine development, berry ripening and stress responses. Altogether this study provides valuable information and robust candidate genes for future functional analysis aiming to clarify mechanisms responsible for the onset of fruit ripening and fruit defense strategies.
Highlights
Transcription factors play an important role in the regulation of plant development and disease response
A total of 50 LATERAL ORGAN BOUNDARIES DOMAIN (LBD) genes having a putatively functional structure were identified in the grapevine genome (Table 1), which is similar to the number of genes identified in Arabidopsis genome (43 genes)[16,17]
LATERAL ORGAN BOUNDARIES (LOB) domain (LBD) transcription factors families have been characterized in several plant species and shown to participate in the regulation of developmental programs and stress responses
Summary
Transcription factors play an important role in the regulation of plant development and disease response. AS2 (LBD6) interacts with AS1 in the process of leaf formation and are known to be required for repression of meristematic genes and establishment of leaf adaxial-abaxial polarity[4] These proteins are involved in the development of sepal and petal primordia of flowers by repressing boundary-specifying genes for normal development of the organ[5]. Functional analysis, mainly in Arabidopsis, rice and maize, revealed that class I LBD genes are mostly involved in plant development such as lateral organ (leaf and flower) development[1,2], and in auxin signal transduction cascade that leads to the formation of lateral roots[7,18,19,20]. The variable C-terminal region of LBD proteins confers transcriptional control on downstream gene expression[14]
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