Figure 3.

LOX Activity and RNA Gel Blot Analysis of Lox1 Class Transcripts in Stolons and New Tubers.

To determine the location of the greatest Lox1 class gene expression in developing tubers, we extracted poly(A)⁺ RNA from three stolon regions of developing new tubers and from unswollen stolon tips. Proximal stolon sections, middle stolon sections, new tuber tips (each ∼1 cm long), and unswollen stolon tips were used. Two micrograms of poly(A)⁺ RNA was loaded in each lane. Hybridization was conducted with the ³²P-labeled 2.1-kb ClaI fragment of the POTLX-1 cDNA clone. Note that expression of the Lox1 class genes in the unswollen tip was approximately the same as that in other parts of the stolon until tuberization was induced (new tuber tip). Magnification is ×1.6 for the photograph of the tuberizing stolon and ×4.2 for the photograph of the unswollen stolon tip. LOX activity was determined as the consumption of oxygen (μmol sec⁻¹ g⁻¹ protein) using linolenic acid as a substrate and a Clark electrode for detection (Royo et al., 1996).