Sterol Changes in Maize Leaves Infected with Helminthosporium carbonum

Abstract

Results of studies with polyene antibiotics have pointed to an interaction with membranes (1). These interactions were reported to occur specifically with sterols (2), and a sparing effect has been noticed upon addition of exogenous sterols (4).It has also been noted that certain phytotoxins produced by plant pathogens interact with plant cell membranes, affecting their permeability and occasionally causing them to rupture (7,12,15). Still other work has implicated sterols in membrane structure (14), and the addition of exogenous sterols was found to exhibit a sparing effect against the action of certain chemicals which induce a loss of electrolytes from plant cells (5).Since permeability may be involved in some mechanisms of disease resistance, it appeared logical to study a particular hostpathogen combination which involved a toxin (13) and to determine what differences, if any, existed in sterol content between healthy and inoculated resistant and susceptible host plants. For this purpose maize and Helminthosporium carbonum (Ullstrup) were chosen as the host-pathogen combination. Susceptible hybrids (PrxK61) and resistant hybrids (Prl X K61) of maize are referred to hereafter as Pr and Prl, respectively. The latter is resistant to both races 1 and 2 of this pathogen but Pr is susceptible to race 1 and resistant to race 2.Culture and inoculation conditions are reported fully elsewhere (6). Forty-eight hours after incubation the plants were harvested. Only infected areas of leaves or comparable areas of control leaves were used. Twenty-five grams of fresh tissue were homogenized in 100 ml of acetone in a Virtis blender, the extract was filtered, and the residue was extracted twice more with 100-ml volumes of acetone. Additional acetone extracts contained no sterols. The acetone extracts were combined and the acetone was evaporated in vacuo, as was done in all other evaporation operations. The remaining aqueous extract was then made 33 I`w ith respect to acetone and extracted four times with 100-ml portions of diethyl ether.The ether phase was washed twice with 50-ml volumes of water, dried over Na2SO4 for 30 min, and evaporated to near dryness. Saponification was accomplished by addition of 50 ml of 95% ethanol and 5 ml of 60% KOH, followed by refluxing for 1 hr. After cooling, 200 ml of water were added and the mixture was then extracted thrice with 100-ml portions of CHCl3. The combined CHCl3 extract was washed twice with 50-ml volumes of water, dried over Na2SO4 for 30 min, evaporated to dryness, and dissolved in 2 ml of CHCl3. After adsorption on 0.5 g of alumina (activity III) the CHCI3 was evaporated. The GLC3 of the eluates showed that the sterols were contained in the 4 and 40yc/ ether fractions. These were combined, evaporated to dryness, and dissolved in 2 ml of CHC13 (fraction I).The aqueous phase from the ether extract was concentrated to 75 ml, and 25 ml of concentrated HCI were added. After refluxing for 3 hr, it was cooled and extracted thrice with 100-ml volumes of benzene. The benzene was ev...

Changes in the Plant β-Sitosterol/Stigmasterol Ratio Caused by the Plant Parasitic Nematode Meloidogyne incognita

“…An increase in C22 desaturase expression levels has been reported as response of Arabidopsis thaliana plants to biotic and abiotic factors: to inducers of PAMP-triggered immunity like flagellin and lipopolysaccharides, to reactive oxygen species (ROS) and osmotic stress as well as to infections with bacterial and fungal pathogens [ 3 , 5 , 14 , 15 , 42 ]. Other than in Arabidopsis , a relative increase in stigmasterol has also been observed in leaves of Triticum aestivum infected by a biotrophic fungus, and in Z. mays leaves infected by a necrotrophic fungus ([ 43 , 44 ].…”

“…However, the repression of SlCYP710A11 expression at 14 and 21 dpi, and the corresponding changes in the β-sitosterol/stigmasterol ratio, contrast with the abovementioned studies, where CYP710A expression was induced, β-sitosterol levels decreased and stigmasterol levels increased. It has to be kept in mind that most previous studies on plant sterol abundance during plant defense focused on shorter time intervals after exposure to pathogens, above-ground plant organs and were conducted mainly on Arabidopsis plants, where β-sitosterol is the most abundant sterol and brassicasterols make up part of the end sterols [ 14 , 15 , 43 , 44 ]. Furthermore, Arabidopsis , like B. juncea , is a member of the Brassicaceae and can produce nematocidal ITCs, which might affect its additional responses to PPN [ 45 ].…”

Identification and Characterization of an S-Adenosyl-L-methionine:Δ24-Sterol-C-methyltransferase cDNA from Soybean

“…Furthermore, suppression of SMT transcripts was observed in soybean cell suspension cultures treated with elicitor. Suppression of sterol biosynthesis and alteration of sterol composition caused by elicitor treatment and pathogen infection have been demonstrated in various plants such as maize, parsley, potato, tobacco, and T. divaricata (Vögeli and Chappell, 1988;Haudenschild and Hartmann, 1995;Brindle et al, 1988;van der Heijden et al, 1989;Jennings et al, 1970).…”

Association of a Specific Cationic Peroxidase Isozyme with Maize Stress and Disease Resistance Responses, Genetic Identification, and Identification of a cDNA Coding for the Isozyme

“…In some cases, there is no evidence for peroxidase involvement in disease resistance in maize ( Zea mays L.) ( , ). However, in other cases, peroxidase disease resistance associations have been reported for maize and have been demonstrated by histochemical evidence (), induction ( − ), and different constitutive isozyme profiles in susceptible versus resistant varieties ( , ).…”