Characterization of the LATERAL ORGAN BOUNDARIES Domain gene family in Vitis vinifera

Abstract

The LATERAL ORGAN BOUNDARIES DOMAIN (LBD) family is a group of plant transcription factors characterized by the presence of a conserved LOB domain, which facilitates DNAbinding. First described in Arabidopsis thaliana, the LBD family has been identified in many plant species and has been seen to play a crucial role in a wide variety of processes, from plant development to the response to biotic and abiotic stresses. Up to nowadays, 50 VviLBD genes have been identified in grapevine.

To further investigate the role of the LBD family in grapevine, we have explored the expression profile of 46 VviLBD genes in 186 samples, coming from 6 organs at different developmental stages, and under abiotic (light-exposed/light-excluded berries) and biotic (inoculation with Plasmopara viticola, the causal agent of downy mildew) stress conditions. The experiment was performed in parallel on two Vitis vinifera cultivars, one susceptible (Pinot noir) and one resistant (Mgaloblishvili) to downy mildew. Gene expression wasmeasured by a TaqMan Gene Expression Assays based on the TaqMan Array Cards technology.

While the expression of most genes was found across different organs, the expression pattern varied among the different developmentalstages and conditions, suggesting the role of specific subsets of these genes as developmental switches. For instance, VviLBDId6 showed regulated expression during berry ripening, whereas other members of the same family responded to the inoculation of P. viticola. Among the genes responding to the biotic stress condition, VviLBDId4 and VviLBDIIa1 were identified, as they display an expression profile typical of susceptibility (S) genes, indicating them as potential novel candidates. In addition, VviLBDIf7 showed an S-gene–like expression profile, and its involvement in the interaction with P. viticola was further validated through the use of dsRNA.

The results obtained present a detailed overview of the role of the LBD members across a wide range of conditions, providing insights relevant to future breeding programs.

Acknowledgements

This work was carried out within the framework of the Grape4vine project (funded by Fondazione Cariplo) and the SMARTBERRY project (funded by PRIN PNRR).