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Article|10 Jun 2022|OPEN
VviAGL11 self-regulates and targets hormone- and secondary metabolism-related genes during seed development
Alessandra Amato1 , Maria Francesca Cardone2 , Nallatt Ocarez3 , Fiammetta Alagna4 , Benedetto Ruperti5 , Chiara Fattorini1 , Riccardo Velasco2 , Nilo Mejía3 , Sara Zenoni1 , and Carlo Bergamini,2 ,
1Department of Biotechnology, University of Verona, 37134 Verona, Italy
2Research Centre for Viticulture and Enology, Council for Agricultural Research and Economics (CREA), 70010 Turi, Italy
3Instituto de Investigaciones Agropecuarias (INIA), Centro Regional de Investigación La Platina, Santiago RM 8831314, Chile
4Trisaia Research Centre, National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), 75026 Rotondella, Italy
5Department of Agronomy, Food, Natural resources, Animals and Environment, University of Padova, 35020 Padova, Italy
*Corresponding author. E-mail: sara.zenoni@univr.it,carlo.bergamini@crea.gov.it

Horticulture Research 9,
Article number: uhac133 (2022)
doi: https://doi.org/10.1093/hr/uhac133
Views: 91

Received: 03 Dec 2021
Accepted: 04 Jun 2022
Published online: 10 Jun 2022

Abstract

VviAGL11, the Arabidopsis SEEDSTICK homolog, has been proposed to have a causative role in grapevine stenospermocarpy. An association between a mutation in the coding sequence (CDS) and the seedless phenotype was reported, however, no working mechanisms have been demonstrated yet. We performed a deep investigation of the full VviAGL11 gene sequence in a collection of grapevine varieties belonging to several seedlessness classes that revealed three different promoter-CDS combinations. By investigating the expression of the three VviAGL11 alleles, and by evaluating their ability to activate the promoter region, we observed that VviAGL11 self-activates in a specific promoter-CDS combination manner.

Furthermore, by transcriptomic analyses on ovule and developing seeds in seeded and seedless varieties and co-expression approaches, candidate VviAGL11 targets were identified and further validated through luciferase assay and in situ hybridization. We demonstrated that VviAGL11 Wild Type CDS activates Methyl jasmonate esterase and Indole-3-acetate beta-glucosyltransferase, both involved in hormone signaling and Isoflavone reductase, involved in secondary metabolism. The dominant-negative effect of the mutated CDS was also functionally ectopically validated in target induction. VviAGL11 was shown to co-localize with its targets in the outer seed coat integument, supporting its direct involvement in seed development, possibly by orchestrating the crosstalk among MeJA, auxin, and isoflavonoids synthesis.

In conclusion, the VviAGL11 expression level depends on the promoter-CDS allelic combination, and this will likely affect its ability to activate important triggers of the seed coat development. The dominant-negative effect of the mutated VviAGL11 CDS on the target genes activation was molecularly validated. A new regulatory mechanism correlating VviAGL11 haplotype assortment and seedlessness class in grapevine is proposed.