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

CARLOS DEZAR,; GABRIELA GAGO,; DANIEL GONZALEZ,; RAQUEL CHAN,

TRANSGENIC RESEARCH

Springer

Lugar: Heidelberg; 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 (sunflower) 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 cauliflower mosaic virus promoter were obtained. Transformed plants show a specific phenotype: they develop shorter stems and internodes, rounder leaves and more compact inflorescences than the non-transformed ones. Shorter stems and internodes are due to a lower rate in cell elongation rather than to a cell division stop. Transgenic plants are more tolerant to water stress conditions, showing improved development, a healthier aspect and higher survival rates than that wild-type plants. Indeed, either under normal or drought conditions, they produce approximately the same seed weight per plant than wild-type plants under normal growth conditions. Plants transformed with a construct that bears the Hahb-4 promoter fused to gus show reporter gene expression in defined cell-types and developmental stages and drought and abscisic acid inducibility. 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.