Crosstalk between jasmonic acid and ethylene pathways are mediated by the HAHB4 transcription factor

MANAVELLA PA, DEZAR CA, CHAN RL

Mar del Plata, Bs As, Argentina

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2007

Plants continuously suffer injuries, both mechanical or as an effect of insects attack. The caused damage led them to generate a fast and strong response that includes the expression of specific genes. Two hormones, jasmonic acid (JA) and ethylene (ET), sometimes acting cooperatively, are also involved in this response. In this work we show that HAHB4 plays a central role in the insects-induced defence response. This sunflower transcription factor is up-regulated when the plants suffer a damage caused by herbivores as indicated by qRT-PCR and transiently transformed leaves with a construct where GUS is fused to the HAHB4 promoter. This gene is also up-regulated by JA and ET following a feedback mechanism. Once enhanced, it positively regulates genes involved in JA synthesis generating a defence response. Target genes levels were quantified in treated and non-treated plants by qRT-PCR indicating that both, a local and a systemic response, are waked up in the presence of HAHB4. Enzymatic measurements show that the accumulation of HAHB4 leads to the formation of green leaf volatiles and trypsin protease inhibitors which trigger a strong defence. In addition, transgenic plants overexpressing this gene show a remarkable tolerance to insect?s attack. In conclusion, HAHB4 mediates the defence against the insect?s attack through a coordination of the JA and ET action in this response.