Hahb-4, a sunflower homeobox-leucine zipper gene, confers drought tolerance to Arabidopsis thaliana plants

DEZAR, C.; GABRIELA MARISA GAGO; GONZALEZ, D.; CHAN, R.

TRANSGENIC RESEARCH

Springer Netherlands

Año: 2005 vol. 14 p. 429 - 440

0962-8819

Homeodomain-leucine zipper proteins constitute a family of transcription factors found only in plants. Hahb-4 is a member of Helianthus annuus (sun.ower) subfamily I. It is regulated at the transcriptional level by water availability and abscisic acid. In order to establish if this gene plays a functional role in drought responses, transgenic Arabidopsis thaliana plants that overexpress Hahb-4 under the control of the 35S Cauli.ower Mosaic Virus promoter were obtained. Transformed plants show a speci.c phenotype: they develop shorter stems and internodes, rounder leaves and more compact in.orescences than their nontransformed counterparts. Shorter stems and internodes are due to a lower rate in cell elongation rather than to a stop in cell division. Transgenic plants were more tolerant to water stress conditions, showing improved development, a healthier appearance and higher survival rates than wild-type plants. Indeed, either under normal or drought conditions, they produce approximately the same seed weight per plant as wild-type plants under normal growth conditions. Plants transformed with a construct that bears the Hahb- 4 promoter fused to gusA show reporter gene expression in de.ned cell-types and developmental stages and are induced by drought and abscisic acid. Since Hahb-4 is a transcription factor, we propose that it may participate in the regulation of the expression of genes involved in developmental responses of plants to desiccation.