Transcript Accumulation of Rice HSP Genes Under Anoxia Conditions.

Plants in the natural environment often have to cope with limited oxygen as a consequence of poor soil drainage, soil compaction or submergence. Oxygen deficiency leads to altered cellular metabolism and can dramatically reduce crop yield. Although flooding is one of the most important environmental stresses worldwide, not all plant species are intolerant to this stress. Most species originating from semi-aquatic environments, such as rice are able to cope with flooding stress and can survive complete submergence for weeks. Abiotic stress responses in plants involve perception mechanisms, signal transduction networks and a large array of stress regulated genes. Among the proteins that have showed response to abiotic stress conditions are heat shock proteins (HSPs) contributing to cellular homeostasis. Studies have been established that plant sHSPs are produced in response to a wide array of environmental stresses. However, it is not clear if HSPs are transcribed as a function of a tolerance mechanism or just are a response under anoxia stress. To elucidate this question, the transcript accumulation of HSPs genes under anoxia stress in two different cultivars, Nipponbare (flooding tolerant) and IPSL 2070 (flooding sensitive) were investigated. Seedling rice roots (15-d-old) from both cultivars were used. Four different treatments were performed: control - without anoxia, seedling under anoxia 24h, seedling under anoxia 48h and seedling under anoxia 72h. ALCOHOL DEHYDROGENASE accumulation transcripts were used to confirm anoxia stress condition. Results obtained showed that both rice cultivars accumulated HSPs gene transcripts under anoxia stress, however majority HSP genes were responsive to anoxia stress in “IPSL2070”, whereas in “Nipponbare”, only six genes were highly upregulated. Most HSPs genes were highly upregulated in the flooding sensitive cultivar when compared to flooding tolerant, suggesting that although HSPs have an important role in the response to anoxia stress, it is not clear if they are directly involved in the tolerance.