Effects of Jasmonic and Salicylic Acids on Cell Division and Cell Cycle Progression

Abstract

HIS STUDY is concerned with the effect of both salicylic and jasmonic acids on mitotic cell division of Allium cepa (Lilliaceae) root tips and their ability to induce chromosomal aberrations. The study also deals with the use of image cytometry and SDS-PAGE techniques to estimate the changes in the cell cycle progression and seed protein banding pattern, respectively. Root tips of Allium cepa (Lilliaceae) treated for 3, 6 and 24 hr. At the cytological level both hormones caused reduction in mitotic index, particularly in roots treated with higher concentrations. A wide range of chromosomal abnormalities such as stickiness, c-metaphase, bridges, chromosome breaks, micronuclei and polyploidy cells were recorded in roots treated with both hormones. The effect of salicylic and jasmonic acids on DNA content corresponding to the proportion of cell cycle phases were calculated. Cytophotometric analysis showed decrease in the proportion of cells with 2C value (G1 phase) and increase in the fraction of cells in S and G2 phases as they compared with control. The lowest concentration of jasmonic acid in root treated for 24 hr and the lowest concentration of salicylic acid in root treated for 3 or 24 hr contradict this result since they increase the number of cells at G1 phase. The effect of both hormones seems to work on G2/M checkpoint at higher concentrations. At the biochemical level jasmonic acid induces changes in the electrophoretic profiles of seed protein of Vicia faba (Fabaceae). These changes include the absence of some bands and the appearance of few novel bands as well as over expression of the others.Keywords: Allium, Vicia, Mitotic index, Chromosomal aberrations, Growth regulators, Image cytometry, SDS-PAGE.Plants need to produce a huge arsenal of chemical compounds to adapt and respond to environmental challenges. Among these compounds, the phytohormones are in prominent position. Plant hormones represent essential link of many plant processes, control a diverse array of plant responses affecting growth and development, either directly or indirectly. Plants respond to biotic and abiotic external stimuli using hormone signal transduction pathways that cause changes in hormone metabolism and in turn cause changes in their distribution within the plant (Davies, 2004).Recently, new classes of plant hormones gained much attention in agriculture, biomedical and industrial application. From these promising hormones are the salicylic and jasmonic acids (Tiryaki, 2004).Salicylic acid (SA) has been recognized as growth regulator of phenolic nature while jasmonic acid is a naturally occurring lipid-derived compound. Jasmonic and salicylic acids play an important role in agriculture through control of different plant processes; such as root growth inhibition (Staswick et al., 1992), seed germination (Corbineau et al.,1988) and the senescence-promoting effect (Parthier, 1990).During the past twenty years, jasmonates have attracted considerable attention. Jasmonic methyl ester plays a vital role as anticancer agents in th...