Functional Characterization of the Medicago HD-Zip transcription factor MTHB1 in the aerial organs

CAPELLA, MATIAS; ARIEL, FEDERICO D; DEZAR, CARLOS A; CHAN, RAQUEL L

San Miguel de Tucuman

Congreso; XLV Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009

MTHB1 is a Medicago truncatula gene encoding a HD-Zip I transcription factor (TF); up-regulated by salt stress and hormones in roots. It was previously reported that this TF acts as a negative regulator of MTLBD1, a LOB-Like TF involved in lateral roots promoting; however, no information is available about the function of this gene in the aerial organs of the plant. The promoter region of MTHB1 was isolated by PCR and cloned into the pKGWFS7 vector directing the expression of the GUS reporter gene. Transgenic Medicago roots were obtained with this construct and were subjected to salt stress and ABA. These experiments indicated that both treatments enhanced MTHB1 expression, in agreement with its potential function. Using the same construct, Arabidopsis plants were transformed and the expression pattern of GUS analyzed by histochemistry. This gene turned out to be expressed in roots, and in certain regions of the SAM. MTHB1 expression pattern is consistent with those of the homologous in Arabidopsis, ATHB7 and 12. TILLING mutant homozygous Medicago plants, unable to express a functional MTHB1, exhibited a particular aerial phenotype with multiple branches in comparison with the WT genotype. The aerial expression pattern, together with the mthb1 plants phenotype, suggests that MTHB1 is somehow involved in branch formation controlling SAM cells fate