Induction of the Arabidopsis PHO1;H10 gene by 12-oxo-phytodienoic acid but not jasmonic acid via a CORONATINE INSENSITIVE1-dependent pathway

Expression of AtPHO1;H10, a member of the Arabidopsis (Arabidopsis thaliana) PHO1 gene family, is strongly induced following numerous abiotic and biotic stresses, including wounding, dehydration, cold, salt, and pathogen attack. AtPHO1; H10 expression by wounding was localized to the cells in the close vicinity of the wound site. AtPHO1; H10 expression was increased by application of the jasmonic acid (JA) precursor 12-oxo-phytodienoic acid (OPDA), but not by JA or coronatine. Surprisingly, induction of AtPHO1; H10 by OPDA was dependent on the presence of CORONATINE INSENSITIVE1 (COI1). The induction of AtPHO1; H10 expression by wounding and dehydration was dependent on COI1 and was comparable in both the wild type and the OPDA reductase 3-deficient (opr3) mutant. In contrast, induction of AtPHO1; H10 expression by exogenous abscisic acid (ABA) was independent of the presence of either OPDA or COI1, but was strongly decreased in the ABA-insensitive mutant abi1-1. The involvement of the ABA pathway in regulating AtPHO1; H10 was distinct between wounding and dehydration, with induction of AtPHO1; H10 by wounding being comparable to wild type in the ABA-deficient mutant aba1-3 and abi1-1, whereas a strong reduction in AtPHO1; H10 expression occurred in aba1-3 and abi1-1 following dehydration. Together, these results reveal that OPDA can modulate gene expression via COI1 in a manner distinct from JA, and independently from ABA. Furthermore, the implication of the ABA pathway in coregulating AtPHO1; H10 expression is dependent on the abiotic stress applied, being weak under wounding but strong upon dehydration.