Plasticity of dhurrin/defence is regulated by methyl jasmonate in Sorghum (Sorghum bicolour)

MN Sohail, C Blomstedt and R Gleadow

School of Biological Sciences, Monash University, 3800 Victoria, Australia

The cyanogenic glucoside, dhurrin plays an important role in growth and defence in sorghum. Previous research has shown close relationship of dhurrin with plant growth and response to herbivory but conclusive studiers were lacking. To check the role of different hormones (involved in plant growth and defence) methyl jasmonate (MeJA) and kinetin were exogenously sprayed on sorghum plants at six leaf stage. Plants were harvested at nine different time points after hormone treatment (0, 12, 24, 48, 72, 96, 120, 144, 168 h) with fifteen plants per treatment per time point. Each plant was split into half and stored for cyanide and RNA analysis at 60 °C drying oven and -80 °C freezer, respectively. To reduce the environmental variation plants were rotated twice a week before hormone application. Due to volatile nature of MeJA, both control and treated plants were covered in bags. Soon after hormone application hydrogen cyanide potential (HCNp) decreased in kinetin treated plants but this trend was also observed in control plants. HCNp started to increase after 48 h but again declined after 72 hours. The MeJA treated plants showed increase in total cyanide potential soon after 12 h of hormone application. This trend kept on increasing until 48 h and then remained almost constant, whereas control plants didn’t show any change in their total cyanide potential throughout the experiment. Right now transcript levels of genes involved in dhurrin regulation are being determined by QPCR. Overall no significant effect of kinetin treatment on dhurrin concentration of sorghum was observed; however MeJA treated plants showed strong response by increased dhurrin concentration.