Anaerobiosis-mediated early transcriptional and translational responses in rice (Oryza sativa L.) coleoptiles and roots

To study the transcriptional and translational responses that occur in rice (Oryza sativa L., cv. Arborio) coleoptiles and roots during the first hours of anoxia, we analysed the patterns of in vitro translational products and in vivo labelled newly synthesized proteins obtained from both organs grown in the presence or absence of O2. Analysis of the protein pattern obtained from nuclear-enriched sub-cellular fractions showed the enhancement of the synthesis of several proteins with molecular weights of 67-62, 54 and 34 kD. In the cytoplasmic-enriched subcellular fractions, we found that the synthesis of polypeptides of relatively low molecular weight (13-16 kD) was strongly induced by anaerobiosis. In vitro translation analysis showed that this enhancement was mainly due to a rapid increase in the level of the corresponding mRNA species. These low-molecular-weight translational products were already detected after 1h of anoxia in both rice roots and rice coleoptiles, but remained undetectable in aerobically grown organs. Additional anaerobic-specific transcriptional and translational changes were also observed. In particular, a specific reduction in the level of mRNAs coding for polypeptides of 38 kD occurred in both roots and coleoptiles after only 1 h of anoxia.