THE TRANSCRIPTION FACTOR AtPHL1 MODULATES SUCROSE TRANSPORT AFFECTING LIPID CONTENT IN ARABIDOPSIS SEEDS

SPIES, FIORELLA; CHAN, RAQUEL LÍA; RAINERI, JESICA

Salta

Congreso; Joint XIV PABMB congressand LV annual SAIB meeting.; 2019

SAIB y PABMB

Plants are continuously subjected to stress situations and they have evolved molecular and physiological responses allowing them to deal with such conditions. Molecular responses mainly occur at the transcriptional level mediated by transcription factors (TFs). Plant TFs are classified in different families and among them, the MYB-CC has been associated to development in response to environmental or nutritional changes. AtPHL1 is a poorly characterized member of the MYB-CC family. It was previously informed that this TF is able to interact with the homeodomain-leucine zipper I TF AtHB23.Aiming at understanding the function of AtPHL1 and the interaction with AtHB23, Arabidopsis plants were transformed with a construct in which the expression of the GUS reporter gene is driven by the promoter of AtPHL1 (prPHL1:GUS). Moreover, we obtained overexpressor (35S:AtPHL1) and mutant homozygous lines (phl1). The analysis of prPHL1:GUS plants indicated that this gene is expressed in roots, in the pedicel-silique node and in the silique funiculus. Phenotyping of phl1 mutant and 35S:AtPHL1 plants showed that the lack of PHL1 (phl1) provoked an early silique opening and e a lesser lipid content in the seeds compared to Col-0 ones. No differences were detected in the glucose, fructose, sucrose and protein seed contents. Phl1 mutant plants also exhibited decreased aerial biomass both in stems and siliques. In view of these differential characteristics, we stated the hypothesis that phl1 mutants have difficulties to transport carbohydrates. To test this hypothesis, we performed a study with the reagent CFDA tracer (5(6)-carboxyfluorescein diacetate, a phloem-mobile probe analog to sucrose) which was transported slower to phl1 siliques compared to control ones. Histological transversal cuts were carried out on stems to investigate xylem morphology. Surprisingly, phl1 plants exhibited a higher number of vascular bundles in the first internode than the WT control. Altogether, the results suggest that PHL1 is a positive regulator of sucrose transport from roots to shoot, particularly to seeds. The decreased lipid content could be the consequence of a slower transport capacity of phl1 plants and could be partially compensated by an increase in the number of vascular bundles in phl1 plants. Further studies will be necessary to corroborate this last hypothesis.