DELLA proteins do not have a key regulatory role in foliar proanthocyanin accumulation in Lotus spp

ESCARAY F.J.; HERNANDEZ-GARCÍA J.; CARRASCO P.; BLAZQUEZ M.A.; RUIZ O.A.

PARANA

Congreso; 54th ANNUAL MEETING SAIB 2018; 2018

SAIB

The MYB-bHLH-WD40 (MBW) complex is considered the master regulator of anthocyanin and proanthocyanin (PA) biosynthesis in different plant species. In A. thaliana, DELLA proteins promote transcriptional activity of the MBW complex by sequestering MYBL2, resulting in increased anthocyanin levels. However, the role of DELLAs in transcriptional regulation of PA biosynthesis has not been evaluated yet. With this objective, we evaluated the effect of paclobutrazol (PBZ) and gibberellic acid (GA3) treatments on foliar PA accumulation in Lotus corniculatus (a species with high levels of PA) and L. tenuis (low levels of PA). Also, we evaluated the expression of DELLA orthologues in both species, and tested protein-protein interaction by Y2H assays between DELLAs and members of the MBW complex that preferentially regulate PA synthesis. Our results showed that PBZ and GA3 treatments affected the growth of Lotus spp.; however, foliar PA levels were not modified in any treatment x genotype (p-value>0.05). Curiously, anthocyanin accumulation increased in leaves of both genotypes treated with PBZ, despite the absence of a MYBL2 orthologue in Lotus, suggesting that DELLAs regulate anthocyanin synthesis by an alternative mechanism in this species. On the other hand, none of the two Lotus DELLAs (orthologous to CRY and LA from Pisum sativum) interacted with the Lotus TT8, TT2b, TT2d, MYBPA2 or MYB5 in Y2H assays. Our results strongly suggest that DELLA proteins do not have a key role in PA biosynthesis regulation in Lotus spp.