Rice response to simultaneous biotic and abiotic stresses

With the predicted climate change and an ever-growing population there is increasing
pressure to develop crop plants with improved stress responses, increased yield and high
nutritive value. We have explored transcriptomic changes in the leaves and roots of rice
plants (Oryza sativa japonica cv Nipponbare) in response to drought and the root-knot
nematode Meloidogyne graminicola. A glasshouse model was developed to mimic
conditions experienced by rice plants in the field. The plant responses under
simultaneous biotic and abiotic stress were dominated by the drought element
accompanied by a unique set of genes that were only responsive to the simultaneous
stress. Highlighted within this group were novel members of stress-responsive gene
families for example cytochrome P450, wall-associated kinases, lipid transfer proteinlike
proteins and new candidate genes that may play important roles in the response of
rice to multiple stresses. The genes that were differentially regulated between the
multiple and the drought stress treatment were explored using loss-of-function mutants.
The loss-of-function mutant for peroxidase precursor gene (per) showed improved
growth and yield compared to the wildtype Nipponbare plants. The experiments
conducted in growth rooms were validated in a field study. Both Nipponbare rice plants,
and the popular lowland indica rice cv IR64 were grown under prolonged vegetative
drought stress accompanied by cyst nematode or root-knot nematode infection.
Reduction of phytate, an anti-nutrient, has been adopted as a major strategy to improve
the nutritional value of crop plants. Nematode susceptibility of low phytate Arabidopsis
plants was studied to determine the effect of reduced phytate content on the plant’s
defence response.
The study has provided insight into the genome-wide transcriptional changes in rice
under a combined biotic and abiotic stress. It has led to better understanding of the
stress responses in plants that will be advantageous in developing crop varieties with
improved yield and nutritive value.