A novel 1 L-myo-inositol-1-phosphate synthase (MIPS, EC 5.5.1.4) gene, designate rcMIPS, was cloned from Ricinus communis. It contained an open reading frame (ORF) of 1669 bp coding for a peptide of 510 amino acids with a molecular mass of 56 kDa. Sequence anaylsis showed high homology compared to other plant MIPS genes, because it contained typical domains owned by MIPS enzymes. The transcript levels of the rcMIPS gene in leaves, stems, and roots were examined after drought stress for 24, 48, and 72 h. The transcript levels in the leaves, stems, and roots increased signifi cantly compared to the control. Results of the enzyme assay showed a signifi cant correlation between the changes of enzyme activity and the transcript levels of the rcMIPS gene in different organs. Decreased relative water contents (RWC) and increased malondialdehyde (MDA) contents in the leaves represented a stress response against drought stress. Our fi ndings suggest that MIPS plays an important role in the defensive mechanisms of R. communis against drought stress.

D-myo-inositol-3-phosphate synthase (MIPS) catalyzes the reaction from D-glucose 6-phosphate to D-myo-inositol 3-phosphate (MIP), which is the first and rate-limiting step in myo-inositol biosynthesis. In this study, Jatropha curcas MIPS cDNA (JcMIPS) (GenBank accession no. EF 185781) has been isolated using mRNA differential display technology (DDRT) and the rapid amplification of cDNA ends (RACE). The cDNA clone of JcMIPS is comprised of 1,957 bp, encoding 509 amino acids, with a predicted molecular weight of 56.4 kDa. The JcMIPS protein is highly homologous to those from other plant species, ranging from 88.4 to 91.18% homology at the amino acid levels. Real-time quantification polymerase chain reaction (PCR) analysis has revealed that JcMIPS transcripts are highly present in seed and leaf tissues, but are at low levels in stem and flower tissues. Furthermore, the transcription of JcMIPS in leaves is up-regulated by abscisic acid (ABA) (100 lM), drought (30% PEG-6000), NaCl (200 mM), and low-temperature (4°C) treatments. The observed increase of JcMIPS enzyme activity is also detected following treatments with ABA, drought, and NaCl. Interestingly, JcMIPS enzyme activity is only slightly changed following low-temperature treatment.

Although the palynology and sporophyte stage of Isöetes sinensis have been well studied, the biology of its gametophyte and embryo is less well understood. To date, the functions of several genes of I. sinensis and the molecular mechanisms of enzymes encoded by them remain to be studied. In the present study, the Fe-SOD gene of I. sinensis was successfully cloned using RT-PCR and rapid amplification of cDNA ends (RACE), and termed IsFeSOD. IsFeSOD has certain reference value in the classification of system evolution. The study also accumulated data for further research on the SOD gene. Bioinformatic analysis was employed to compare IsFeSOD with gene sequences obtained from other plants present in the GenBank. Furthermore, the recombinant pET32-FeSOD plasmids were transformed into Escherichia coli BL21 for expression. IsFeSOD was observed to have 1469 nucleotides that were predicted to encode 247 amino acids. The bioinformatic analysis revealed that IsFeSOD contained conserved TGGGA sequences, similar to eight other species, in addition to five other conserved sequences. The recombinant protein was about 43 kDa. Recombinant FeSOD was expressed, purified, and confirmed by western blotting. Alignment of complete Fe-SOD mRNA sequences from 9 species revealed several conserved sequences. A phylogenetic tree was constructed using MEGA4.1 and ClustalX multiple-sequence alignment programs. This study could be helpful in further characterization of SOD genes and for classification of system evolution status.