MBW complexes impinge on anthocyanidin reductase gene regulation for proanthocyanidin biosynthesis in persimmon fruit

[EN] MBW protein complexes containing MYB, bHLH and WD40 repeat factors are known transcriptional regulators of secondary metabolites production such as proanthocyanidins and anthocyanins, and developmental processes such as trichome formation in many plant species. DkMYB2 and DkMYB4 (MYB-type), DkMYC1 (bHLH-type) and DkWDR1 (WD40-type) factors have been proposed by different authors to take part of persimmon MBW complexes for proanthocyanidin accumulation in immature fruit, leading to its characteristic astringent flavour with important agronomical and ecological effects. We have confirmed the nuclear localization of these proteins and their mutual physical interaction by bimolecular fluorescence complementation analysis. In addition, transient expression of DkMYB2, DkMYB4 and DkMYC1 cooperatively increase the expression of a persimmon anthocyanidin reductase gene (ANR), involved in the biosynthesis of cis-flavan-3-ols, the structural units of proanthocyanidin compounds. Collectively, these data support the presence of MBW complexes in persimmon fruit and suggest their coordinated participation in ANR regulation for proanthocyanidin production.This work was funded by the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA)-FEDER (grant no. RF2013-00043-C02-02 and RTA2017-00011-C03-01). FG-M was funded by a fellowship co-financed by the Generalitat Valenciana and European Social Fund (2014 2020) (grant no. ACIF/2016/115).Gil Muñoz, F.; Sanchez Navarro, JA.; Besada Ferreiro, CM.; Salvador Perez, AA.; Badenes Catala, M.; Naval Merino, MDM.; Rios Garcia, G. (2020). MBW complexes impinge on anthocyanidin reductase gene regulation for proanthocyanidin biosynthesis in persimmon fruit. Scientific Reports. 10:1-11. https://doi.org/10.1038/s41598-020-60635-wS11110Dixon, R. A., Xie, D.-Y. & Sharma, S. B. Proanthocyanidins–a final frontier in flavonoid research? New Phytol. 165, 9–28 (2005).Yonemori, K. & Matsushima, J. 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A cross population between D. kaki and D. virginiana shows high variability for saline tolerance and improved salt stress tolerance

[EN] Persimmon (Diospyros kaki Thunb.) production is facing important problems related to climate change in the Mediterranean areas. One of them is soil salinization caused by the decrease and change of the rainfall distribution. In this context, there is a need to develop cultivars adapted to the increasingly challenging soil conditions. In this study, a backcross between (D. kaki x D. virginiana) x D. kaki was conducted, to unravel the mechanism involved in salinity tolerance of persimmon. The backcross involved the two species most used as rootstock for persimmon production. Both species are clearly distinct in their level of tolerance to salinity. Variables related to growth, leaf gas exchange, leaf water relations and content of nutrients were significantly affected by saline stress in the backcross population. Water flow regulation appears as a mechanism of salt tolerance in persimmon via differences in water potential and transpiration rate, which reduces ion entrance in the plant. Genetic expression of eight putative orthologous genes involved in different mechanisms leading to salt tolerance was analyzed. Differences in expression levels among populations under saline or control treatment were found. The 'High affinity potassium transporter' (HKT1-like) reduced its expression levels in the roots in all studied populations. Results obtained allowed selection of tolerant rootstocks genotypes and describe the hypothesis about the mechanisms involved in salt tolerance in persimmon that will be useful for breeding salinity tolerant rootstocks.This study was funded by the IVIA and the European Funds for Regional Development. F. G.M.was funded by a PhD fellowship from the European Social Fund and the Generalitat Valenciana (ACIF/2016/115). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.Gil Muñoz, F.; Pérez-Pérez, JG.; Quiñones, A.; Primo-Capella, A.; Cebolla Cornejo, J.; Forner Giner, MA.; Badenes Catala, M.... (2020). A cross population between D. kaki and D. virginiana shows high variability for saline tolerance and improved salt stress tolerance. PLoS ONE. 15(2):1-27. https://doi.org/10.1371/journal.pone.0229023S127152Visconti, F., de Paz, J. M., Bonet, L., Jordà, M., Quiñones, A., & Intrigliolo, D. S. (2015). Effects of a commercial calcium protein hydrolysate on the salt tolerance of Diospyros kaki L. cv. «Rojo Brillante» grafted on Diospyros lotus L. Scientia Horticulturae, 185, 129-138. doi:10.1016/j.scienta.2015.01.028Forner-Giner, M. A., & Ancillo, G. (2013). Breeding Salinity Tolerance in Citrus Using Rootstocks. Salt Stress in Plants, 355-376. doi:10.1007/978-1-4614-6108-1_14Visconti, F., Intrigliolo, D. 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