The Lipoxygenase Isozymes in Soybean [Glycine max (L.) Merr.] Leaves (Changes during Leaf Development, after Wounding, and following Reproductive Sink Removal)

Abstract

The levels of individual lipoxygenase isozymes in soybean [Clycine max (1.) Merr.] leaves were assessed during leaf development, after mechanical wounding, and i n response to reproductive sink removal. Native isoelectric focusing followed by immunoblotting was employed to examine individual lipoxygenase isozymes. In leaves of all ages, two distinct classes of lipoxygenase isozymes were detected. One class of lipoxygenase isozymes had nearly neutral isoelectric points (pls) ranging from pH 6.8 to 7.2. The other class of lipoxygenase isozymes had acidic pls ranging from pH 4.7 to 5.6. During leaf development, all of the neutral lipoxygenase isozymes and most of the acidic isozymes were present in greatest abundance in the youngest leaves examined and declined in amount as leaf age increased. However, four acidic lipoxygenase isozymes (pl = 4.70, 4.80, 4.90, 4.95) were more abundant in intermediateage leaves than in either the youngest or oldest leaves examined.Following mechanical wounding of leaves, these same four acidic isozymes also increased i n abundance both locally and systemically in leaves from wounded plants. Unlike the specific effects of wounding on the lipoxygenase isozymes in leaves, reproductive sink removal stimulated a general increase in most of the acidic lipoxygenase isozymes in leaves.

The Differential Expression of Wound-Inducible Lipoxygenase Genes in Soybean Leaves

“…Prior to attempting to identify wound-inducible lipoxygenase genes, a comprehensive examination of lipoxygenase activity, protein, and total transcript levels during soybean leaf development was conducted. Generally, lipoxygenase activity, protein, and transcript levels were highest in young leaves and declined as leaf age increased (Saravitz, 1993). A similar developmental pattern has been reported for lipoxygenase isozyme levels in first trifoliate leaves of soybean (Saravitz and Siedow, 1995).…”

“…Increased lipoxygenase expression has been detected in plants during or following a variety of stresses, including insect feeding (Hildebrand et al, 1989), infection by both bacterial and funga1 pathogens (Yamamoto and Tani, 1986;Keppler and Novacky, 1987;Croft et al, 1990;Kato et al, 1992;Koch et al, 1992;Fournier et al, 1993;Melan et al, 1993), low water potential (Bell and Mullet, 1991), and mechanical wounding (Hildebrand et al, 1989;Mullet, 1991, 1993;Geerts et al, 1994;Saravitz and Siedow, 1995). Although the physiological relevance of stress-associated increases in lipoxygenase has yet to be established, severa1 proposals have been made, including membrane degradation during hypersensitive resistance responses (Croft et al, 1990), production of fatty acid-derived, antimicrobial molecules (Ohta et al, 1990(Ohta et al, , 1991Kato et al, 1992;Croft et al, 1993), and the stress-associated synthesis of plant growth substances such as ABA (Creelman et al, 1992a) and JA Koch et al, 1992).…”

Subcellular Localization of Celery Mannitol Dehydrogenase (A Cytosolic Metabolic Enzyme in Nuclei)

“…The fractionated proteins were electrotransferred to nitrocellulose membranes (NitroPure, Micron Separations Inc., Westborough, MA) using a transfer apparatus (Hoefer Scientific Instruments, San Francisco, CA) in transfer buffer (25 mM Tris, 192 mM Gly, 0.1% [w/v] SDS, pH 8.5) at 300 mA overnight. Immunoblot analyses were performed according to Saravitz and Siedow (1995) with minor modification. The nitrocellulose was treated as follows: blocking in a blocking solution (5% nonfat dry milk in TBST), washing in TBST (2 X 1 min, 15 min, 2 X 5 min), incubation with antiserum (1:10,000 for anti-MTD, 1:64,000 for anti-HMGa in blocking solution, preincubated 30 min), washing in TBST (2 X 1 min, 15 min, 3 X 5 min), incubation with secondary antibodies (goat anti-rabbit IgG-horseradish peroxidase, human/mouse adsorbed, [Southern Biotechnology Associates, Inc., Birmingham, ALI, diluted 1:5000 in TBST), and washing in TBST (2 X 1 min, 15 min, 4 X 5 min).…”

Lipoxygenase Is Involved in the Control of Potato Tuber Development

“…LOX isozyme profiles change quantitatively and qualitatively during soybean leaf development (Saravitz and Siedow, 1995) and during seed germination in cucumbers (Matsui et al., 1992; Feussner et al, 1996). In addition, many LOX genes are regulated differentially during Arabidopsis seedling development (Melan et al, 1994), pea nodule formation (Wisniewski et al, 1999), tomato fruit ripening (Ferrie et al, 1994; Kausch and Handa, 1997), potato tuber development (Bachem et al, 1996), and pea carpel development (Rodriguez-Concepcion and Beltran, 1995).…”