An anaerobically inducible early (aie) gene family from rice

One of the major abiotic stresses that affect plant growth and development is anoxia or hypoxia. Plants respond to anoxia by regulation of gene expres sion at both the transcriptional and translational levels. Genes involved i n such regulation are expected to be expressed soon after onset of anoxia. To date, however, anaerobically regulated genes that have been characterize d predominantly encode enzymes for sugar phosphate metabolism, and are indu ced after several hours of anaerobic conditions. Early induced genes, those responding after 1-2 h of anoxia, have not been studied extensively. To st udy the early anaerobic response we investigated the most flooding-tolerant variety of rice, FR13A (flood-resistant). We used differential display tec hniques to identify cDNA fragments representing mRNAs that are induced with in 90 min of anoxia. We isolated two cDNA fragments and one full-length cDN A that were induced to high levels. These cDNAs were found to be members of a family of 2-3 genes, which were called the aie (anaerobically inducible early) gene family. Northern blot analyses showed that the mRNA levels of a ie genes peaked after 1.5 to 3 h of anoxia and were still at high levels af ter 72 h of anoxia. RNase protection assays showed 4-5 different protected bands indicating multiple transcripts from the aie gene family. Sequence an alyses of the full-length cDNA showed an open reading frame that putatively encodes a 14 kDa protein of 127 amino acid residues. Neither the nucleotid e nor the deduced amino acid sequences of this gene showed any significant homology to any known genes or proteins present in the GenBank or SwissProt databases. This novel gene, that is induced so early under anoxia in plant s, may play an important role in plant metabolism under anaerobic condition s.