AtHB5 is involved in source-to-sink transport of sugar in Arabidopsis

RAMINGER BETINA LORENA; MIGUEL, VIRGINIA N; CHAN RAQUEL L.; CABELLO JULIETA V.

Paraná

Congreso; LIV Reunión anual de la SAIB; 2018

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

AtHB5 is a HD-Zip I transcription factor (TF) from Arabidopsis thaliana. It was previously reported that a group of HD-Zip I TFs modified its expression during lignification process in Arabidopsis stems. Interestingly, while AtHB7 and AtHB12 increased its expression during stem maturation, AtHB5 decreased it and it was the only HD-Zip I that exhibited this behavior. To investigate its biological function, mutants and overexpressing lines (OE) were obtained. In athb5, AtHB7, AtHB12, AtHB6 and AtHB16 were down-regulated, while in OE they were up-regulated. A phenotypic analysis showed that athb5 had wider and more lignified stems, while OE had narrow and less lignified stems than WT. Furthermore, athb5 stems exhibit more phloem and xylem vessels than WT as well as in vascular tissue from leaves and pedicel. Also OE had more glucose and sucrose on rosette leaves than WT but less on cauline leaves. Moreover, aniline blue staining showed that OE had more callose in rosette leaves than WT, indicating a defective sugar transport. Regarding to root system, under normal conditions athb5 had larger roots while OE had shorter roots than WT. Furthermore, under complete dark conditions there were no differences between genotypes, but when they were supplemented with sucrose, athb5 exhibited larger roots than WT and OE shorter. Arabidopsis plants were transformed with AtHB5 promoter fused to GUS reporter, and preliminary results indicated expression in hypocotyl and vascular tissue.Altogether these results suggest that AtHB5 is a negative regulator of some HD ?Zip TFs and it is implicated in source-to-sink transport of sugar in Arabidopsis