Identification and partial characterisation of a putative novel plant stress response gene from Arabidopsis thaliana.

Abstract

Exposure of plants to stress results in the expression of plant genes whose products play a role in defence responses against the stress. Stress stimuli to which plants may be exposed are wounding, drought, salinity, excessive light intensity, heat stress, pathogens, biotic and abiotic factors that lead to the accumulation of H2O2, salicylic acid and plant hormones e.g absiscic acid. This study describes the identification and partial characterisation of a putative novel gene from Arabidopsis thaliana, named the DIINN gene. The sequence of the predicted protein encoded by the DWNN gene shows similarity to a gene isolated from Chinese hamster ovary cells that were resistant to chemically induced programmed cell death. Since programmed cell death is one of the processes involved in plant defence responses to stress, it is hypothesised that the DWNN gene may also play a role in plant programmed cell death. The protein product encoded by the DWNN gene, DWNN, shows homology to proteins from diverse species and phyla. Plants transformed to overexpress DWNN show severely stunted growth and abnormal developmental patterns while plants in which DWNN has been knocked out show an accelerated growth rate. Analysis of the expression pattem of the DLI/NN gene using the GUS gene reporter system suggests that the DWNN gene is expressed in secondary lignification during xylogenesis and in wounded plant tissue. Both xylogenesis and wounding are processes known to involve progralnmed cell death and the regulation of protein turnover.