HAHB10, a sunflower HD-Zip II transcription factor, participates in the induction of flowering and in the control of phytohormone-mediated responses to biotic stress

DEZAR CA; GIACOMELLI JI; MANAVELLA PA; RE DA; ALVES FERREIRA M; BALDWIN IT; BONAVENTURE G; CHAN RL

JOURNAL OF EXPERIMENTAL BOTANY

OXFORD UNIV PRESS

Año: 2011 vol. 62 p. 1061 - 1076

0022-0957

  The transcription factor HAHB10 belongs to the sunflower (Helianthus annuus) HD-Zip II subfamily and it has been previously associated with the induction of flowering (Rueda et al., 2005). In this study we show that HAHB10 is expressed in sunflower leaves throughout the vegetative stage and in stamens during the reproductive stage. In a short-day inductive condition the expression of this gene is induced in shoot apexes together with the expression of the flowering genes HAFT and HAAP1. Transgenic Arabidopsis plants expressing the HAHB10 cDNA either under the regulation of its own promoter or CaMV35S exhibited an early flowering phenotype. This phenotype was completely reverted in a non-inductive light regime, indicating a photoperiod-dependent action for this transcription factor. Gene expression profiling of Arabidopsis plants constitutively expressing HAHB10 indicated that specific flowering-transition genes, such as FT, FUL and SEP3 were several fold induced whereas genes related to biotic stress responses, such as PR1, PR2, ICS1, AOC1, EDS5, and PDF1-2a were repressed. The expression of HAHB10 and the flowering genes HASEP3 and HAFT was up-regulated by both SA treatments and infection with a virulent strain of Pseudomonas syringae. Basal SA and JA levels in Arabidopsis plants ectopically expressing HAHB10 were similar to control plants however SA levels differentially increased in the transgenics after wounding and infection with P. syringae while JA levels differentially decreased. Together, the results indicated that HAHB10 participates in two different processes in plants: the transition from the vegetative to the flowering stage via the induction of specific flowering transition genes and the accumulation of phytohormones upon biotic stresses.