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

SPIES, FIORELLA; RAINERI, JESICA; CHAN, RAQUEL L.

Congreso; SAIB; 2019

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 GUS reporter gene is driven by the promoter of AtPHL1 (prPHL1:GUS). Moreover, we obtained overexpressor (OE) and mutant homozygous lines (phl1). The analysis of in prPHL1:GUS plants indicated that this gene is expressed in roots, in the pedicel-silique node and in the silique funiculus. Phenotyping of mutant and OE plants showed that phl1 plants opened earlier the siliques and the seeds have a lesser lipid content compared to Col-0 ones. No differences were detected in the glucose, fructose, sucrose and protein contents. Mutant phl1 plants also exhibited decreased aerial biomass content, in stems and siliques. In view of these differential phenotypes, we stated the hypothesis that phl1 mutants have difficulties to transport carbohydrates. A study performed with SU tracer (a sugar transport marker) showed a slower transport in phl1 siliques compared to control plants. Surprisingly, phl1 plants also exhibited higher number of vascular bundles in the first internode of stems, compared to WT plants. 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 compensated by a higher number of vascular bundles in phl1 plants. Further studies will be necessary to corroborate this hypothesis.