Manipulation of VviAGL11 expression changes the seed content in grapevine (Vitis vinifera L.).

Seedlessness in grapes is a desirable trait, especially for in natura consumption. Previously, we showed that VviAGL11 is the main responsible gene for seed morphogenesis in grapevine. Here we tested the function of this gene in grapevine with the use of plant plasmids. VviAGL11 was cloned into silencing and overexpression versions of p28iIR plasmid. Reproductive grapevine bunches from different seeded and seedless cultivars were separately treated with VviAGL11-harboring plasmids, along with controls. Plasmids were detected in leaves after a month of treatment, and berries, leaves, stems and seeds were analyzed for ectopic gene expression by RT-qPCR after 90 days of plasmid injection. Fruits from the seedless 'Linda' treated with the VviAGL11-overexpression plasmid showed high expression levels of VviAGL11 and exhibited small seeds that were not found in the untreated control samples. Mature grapes from seeded 'Italia' and 'Ruby' bunches treated with the VviAGL11-silencing plasmid showed decreased VviAGL11 expression, reduced number of seeds and increased number of seed traces. The present study confirms that VviAGL11 is a key master regulator of seed morphogenesis in grapevine and corroborates with the applicability of plant plasmids as promising biotechnological tools to functionally test genes in perennial plants in a rapid and confident way.

The MADS-box gene Agamous-like 11 is essential for seed morphogenesis in grapevine.

Despite the wide appreciation of seedless grapes, little is known about the molecular mechanisms that drive the stenospermocarpic seedless-type phenotype in grapevine. In order to address the molecular mechanisms that control seedlessness in grapevine, our study aimed to characterize VviAGL11, a class D MADS-box transcription factor gene that has been proposed as the major candidate gene involved in Vitis vinifera seed morphogenesis. VviAGL11 allelic variations in seeded and seedless grapevine cultivars were determined, and its correlations with allele-specific steady-state mRNA levels were investigated. VviAGL11 relative expression was significantly higher in seeds at 2, 4, and 6 weeks after fruit set, whereas in the seedless grape its transcript levels were extremely low in all stages analyzed. In situ hybridization revealed transcript accumulation specifically in the dual endotesta layer of the seeds, which is responsible for elongation and an increase of cell number, a necessary step to determine the lignification and the final seed size. No hybridization signals were visible in the seedless grapevine tissues, and a morphoanatomical analysis showed an apparent loss of identity of the endotesta layer of the seed traces. Ectopic expression of VviAGL11 in the Arabidopsis SEEDSTICK mutant background restored the wild-type phenotype and confirmed the direct role of VviAGL11 in seed morphogenesis, suggesting that depletion of its expression is responsible for the erroneous development of a highly essential seed layer, therefore culminating in the typical apirenic phenotype.

Sak1 kinase interacts with Pso2 nuclease in response to DNA damage induced by interstrand crosslink-inducing agents in Saccharomyces cerevisiae.

By isolating putative binding partners through the two-hybrid system (THS) we further extended the characterization of the specific interstrand cross-link (ICL) repair gene PSO2 of Saccharomyces cerevisiae. Nine fusion protein products were isolated for Pso2p using THS, among them the Sak1 kinase, which interacted with the C-terminal ß-CASP domain of Pso2p. Comparison of mutagen-sensitivity phenotypes of pso2Δ, sak1Δ and pso2Δsak1Δ disruptants revealed that SAK1 is necessary for complete WT-like repair. The epistatic interaction of both mutant alleles suggests that Sak1p and Pso2p act in the same pathway of controlling sensitivity to DNA-damaging agents. We also observed that Pso2p is phosphorylated by Sak1 kinase in vitro and co-immunoprecipitates with Sak1p after 8-MOP+UVA treatment. Survival data after treatment of pso2Δ, yku70Δ and yku70Δpso2Δ with nitrogen mustard, PSO2 and SAK1 with YKU70 or DNL4 single-, double- and triple mutants with 8-MOP+UVA indicated that ICL repair is independent of YKu70p and DNL4p in S. cerevisiae. Furthermore, a non-epistatic interaction was observed between MRE11, PSO2 and SAK1 genes after ICL induction, indicating that their encoded proteins act on the same substrate, but in distinct repair pathways. In contrast, an epistatic interaction was observed for PSO2 and RAD52, PSO2 and RAD50, PSO2 and XRS2 genes in 8-MOP+UVA treated exponentially growing cells.

Identification and expression analysis of genes associated with the early berry development in the seedless grapevine (Vitis vinifera L.) cultivar Sultanine.

Sultanine grapevine (Vitis vinifera L.) is one of the most important commercial seedless table-grape varieties and the main source of seedlessness for breeding programs around the world. Despite its commercial relevance, little is known about the genetic control of seedlessness in grapes, remaining unknown the molecular identity of genes responsible for such phenotype. Actually, studies concerning berry development in seedless grapes are scarce at the molecular level. We therefore developed a representational difference analysis (RDA) modified method named Bulk Representational Analysis of Transcripts (BRAT) in the attempt to identify genes specifically associated with each of the main developmental stages of Sultanine grapevine berries. A total of 2400 transcript-derived fragments (TDFs) were identified and cloned by RDA according to three specific developmental berry stages. After sequencing and in silico analysis, 1554 (64.75%) TDFs were validated according to our sequence quality cut-off. The assembly of these expressed sequence tags (ESTs) yielded 504 singletons and 77 clusters, with an overall EST redundancy of approximately 67%. Amongst all stage-specific cDNAs, nine candidate genes were selected and, along with two reference genes, submitted to a deeper analysis of their temporal expression profiles by reverse transcription-quantitative PCR. Seven out of nine genes proved to be in agreement with the stage-specific expression that allowed their isolation by RDA.