Poster: Lipids & Related Molecules

Abs # 868: Jasmonic acid levels in senescing leaves of LOX-suppressed Arabidopsis mutants.

Presenter:	Fukushige, Hirotada , hfuku1@uky.edu
Authors	Fukushige, Hirotada  (A)   Cai, Zhaohui  (B)   Hildebrand, David F (A)   Gan, Susheng  (C)
Affiliations:	(A): Department of Agronomy, University of Kentucky (B): Kentucky Tobacco Reseach and Development Center, University of Kentucky (C): Department of Horticulture, Cornell University

We have previously showed that jasmonic acid (JA) levels increased in senescing leaves of Arabidopsis and found that the transcript level of Lipoxygenase 1 (LOX1) goes up while that of LOX2 decreases (He et al. 2002 Plant Physiol. 128:876-884). To investigate potential role of these LOXs in JA biosynthesis, we obtained 2 lines of lox1 knockout mutants (lox1-1 and lox1-2) by using the Wisconsin Gene Machine Facility and the LOX2-suppressed line from the Arabidopsis Biological Resource Center. We measured JA levels in senescing leaves of these mutant lines. JA levels in young leaves are about 10 pmol/g fresh weight (f.w.) in both lox1-1, lox1-2 lines and wild type (WT; ecotype WS). In senescing leaves, the JA levels increased to 510, 150, and 1,400 pmol/g f.w. in lox1-1, lox1-2 and WT, respectively; the JA levels were lower in senescing leaves of the knockout lines than WT. On the other hand, no JA could be detected in senescing leaves of the lox2-suppressed line while the level increased to 650 pmol/g f.w. in vector control plants (ecotype Columbia). These data suggest that both LOX1 and LOX2 catalyze JA synthesis in senescing Arabidopsis leaves with LOX2 being much more significant.