Regulation of flowering time in Brachypodium distachyon

GONZALO, LUCÍA; MACHADO, RODRIGO; EUSEBI, DELFINA; GÜNTHARDT, MARÍA MARGARITA

Huesca

Conferencia; 4th International Brachypodium Conference 2019; 2019

Botanical Society of America

Regulation of flowering time in Brachypodium distachyonLucía Gonzalo(1), Rodrigo Machado(1), Delfina Eusebi(1), María Margarita Günthardt(1), Sebastian E. Muchut(1), Andrea G. Reutemann(1), Abelardo C. Vegeti(1), John P. Vogel(2), Nora G. Uberti Manassero(1)(1) Laboratorio de Biología Evolutiva y Molecular de Plantas (BEMP), Facultad de Ciencias Agrarias, Universidad Nacional del Litoral, Argentina (2) Joint Genome Institute ? DOE, USAIn higher plants, phase transition from vegetative to reproductive development is tightly coordinated through networks that integrate internal and external stimuli. PANICLE PHYTOMER2 (PAP2) is a SEPALLATA-like protein that plays an important role in regulating rice meristems and floral organ identity (Kobayashi et al., 2012). It promotes the phase changes of the shoot apical meristem from vegetative to inflorescence meristem, acting together with AP1-like proteins to negatively regulate RCN4 (TFL1 orthologue) in a conserved pathway between Arabidopsis thaliana and rice (Liu et al., 2013). In this work, we study the role of the Brachypodium distachyon gene BdPAP2 in regulating flowering time. In order to achieve this goal, we first over-expressed BdPAP2 in A. thaliana plants. Transgenic plants showed an earlier transition from vegetative to reproductive state and, consequently, developed fewer rosette leaves than control plants. This phenotype was correlated with increased expression levels of the floral integrators SOC1 and FT. Interestingly, TFL1 expression levels were significantly reduced in these plants, suggesting a possible functional conservation in the pathway reported for A. thaliana and rice. We also analyzed two independent BdPAP2 mutant lines of B. distachyon. One of the lines carries a T-DNA insertion that introduced a 4xCaMV35S enhancer sequence in an intron of BdPAP2, upregulating its expression. This activation tagged line flowered earlier and developed fewer leaves than control plants. The other mutant was a sodium azide mutant that contains a SNP mutation in a splice-site donor that is expected to disrupt BdPAP2 function. As expected, this mutant showed a delay in flowering time. Our results obtained in A. thaliana and B. distachyon suggest that BdPAP2 controls flowering time by regulating the B. distachyon TFL1 orthologue, BdRCN4. As a first attempt to test this hypothesis, we studied the 3` distal region of TFL1 homologues of B. distachyon. We found the putative regulatory boxes in all the three genes analyzed, in a similar number and disposition of those found in A. thaliana. We are now focusing our efforts in corroborating if BdRCN4 is a direct target of BdPAP2, as well as if this regulation depends on the interaction of BdPAP2 and AP1-like proteins. This research will shed new light on the pathways that regulate flowering time in grasses.References:The Plant Cell Online, 2012, 24(5), 1848.Developmental Cell, 2013, 24, 612.