CROSSTALK BETWEEN JASMONIC ACID AND ETHYLENE PATHWAYS ARE MEDIATED BY THE HAHB4 TRANSCRIPTION FACTOR

MANAVELLA PA, DEZAR CA, BONAVENTURE G, BALDWIN TI AND CHAN RL

Aguas de Lindóia, São Paulo, Brazil

Congreso; XXXVII Annual Meeting of Brazilian Society for Biochemistry and Molecular Biology (SBBq) and XI Congress of the Panamerican Association for Biochemistry and Molecular Biology (PABMB); 2008

Abstract: 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 defense 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 theHAHB4 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 defense 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 defense. In addition, transgenic plants overexpressing this gene show a remarkable tolerance to insect's attack which could be used as a biotechnological weapon to deal with insect plagues. In conclusion, HAHB4 mediates the defense against the insect's attack through a coordination of the JA and ET action in this response.