Structure, activity, expression, and localization of 13-LOX in chloroplasts. (A) Domain structure of 13-LOX and 13-LOX-ΔTP. (B) Activity of 13-LOX and 13-LOX-ΔTP on LA, LeA, and ARA. (C) Expression of 13-LOX in MeJA-treated plants and during natural senescence (C, a) and immunodetection of the enzyme in outer envelope exoplasmic faces (OE-EF) (yellow circles) and inner envelope protoplasmic faces (IE-PF) (green boxes) obtained after freeze-fracturing chloroplasts of MeJA-treated leaves using 13-LOX antibodies and 10-nm gold-conjugated secondary antibodies (C, b). (D) Immunolocalization of 13-LOX in the inner plastid envelope. Controls show markers for outer envelope membranes (OM), inner envelope membranes (IM), and mixed outer and inner envelope membranes (ME), as well as thylakoids (Th) and stroma (St).