Hahb10 sunflower transcription factor is involved in phytohormone mediated response to biotic stress

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

San Miguel de Tucumán, Tucumán, Argentina

Congreso; XLV Reunión Anual (SAIB); 2009

SAIB

The transcription factor HAHB10 belongs to the sunflower HD-Zip II subfamily and it has been previously associated with the induction of flowering. A gene expression analysis performed with HAHB10-constitutively expressing Arabidopsis plants indicated that specific flowering transition genes, such as FT, AGL8 and AGL9 were several fold induced whereas genes related to biotic stress responses, such as PR1, PR2, ICS1, AOC1, EDS5, PDF1-2a, were repressed. Specific gene induction and repression was validated by qRT-PCR, both in Arabidopsis transgenic plants and in transiently transformed sunflower leaf discs. The expression of HAHB10 and the flowering genes HAAGL9 and HAFT was up regulated by both SA treatments and infection with a virulent strain of Pseudomonas syringae. Together, the results indicated that HAHB10 participates in the induction of flowering and defense responses by activating and repressing respectively specific genes involved in these two processes. On the other hand, 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. Moreover, arabidopsis plants co-expressing 35S:HAHB10 and 35S:NahG also showed early flowering, suggesting that HAHB10 acts downstream of SA signaling.