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Pentatricopeptide repeat protein (PPR) proteins are putative RNA-binding proteins which are particularly prevalent in terrestrial plants. Previous research has reported the great difficulty in purifying soluble PPR proteins in Escherichia coli, therefore hindering further study of their functions. In this paper, we report the use of the pMAL ™ prokaryotic expression system to acquire a soluble expression of a PPR protein, RF1A from rice (Oryza sativa L.). After purification, we identified RF1A by ESI-TOF-MS/MS. We also made an estimation of its secondary structure using the circular dichroism spectroscopy. These results supported the bioinformatic prediction of helical-hairpin model about PPR proteins.

Cold tolerance at early seedling stage of rice ( Oryza sativa L.) is one of the major determinants for the stable stand establishment in temperate and high-elevation areas. In the current study, with 269 recombinant inbred lines derived from a cross between a japonica tolerant to cold and a sensitive indica of rice, the cold tolerance at early seedling stage was evaluated by the paper-roll tests in a two-replication trial with 10- and 13-day treatments at 10 °C, respectively. The phenotype data, in combination with a complete linkage map consisting of 198 marker loci, were used to conduct composite interval mapping to locate both main-effect and digenic epistatic QTL for the trait. Three main-effect QTL were identified. The comparison of the QTL identified in these two cold treatments resulted in an intriguing finding that seedling cold tolerance in the 10-day cold treatment was regulated by many loci each with minor effect while that in the 13-day cold treatment was controlled by a major QTL as well as minor ones. Of the three main-effect QTL, QTL qSCT-11 , closely linked to microsatellite marker RM202 on chromosome 11, was found to increase its additive effect from 4.07 to 10.11% (seedling survival percentage) as the duration of cold stress was prolonged from 10 days to 13 days. In the 13-day cold treatment, QTL qSCT-11 was detected at a very high LOD score of 19, explaining up to 30% of the phenotypic variation. In addition, a total of nine digenic interactions were detected, each showing small effects on cold tolerance with R 2 ranging from 3.5 to 9.7%, with an average R 2 of 5.3%. In the 13-day cold treatment, the sum of absolute epistatic effects of all the interactions amounted up to 36% in seedling survival percentage, suggesting the importance of epistasis in the genetic control of cold tolerance. These results would favor our better understanding of the genetic control of cold tolerance in rice. The identification of QTL for the trait is important for the development of rice cultivars with a broader climatic adaptation.

A primary physical map of rice chromosome 12 was constructed using marker-based chromosome landing and chromosome walking. A BAC library from IR64 was screened using 84 RFLP markers, 4 STS markers and 6 microsatellite markers on chromosome 12 by colony hybridization and polymerase chain reaction (PCR) amplification. A total of 59 contigs consisting of 419 BAC clones including 5 single-clones were physically aligned on rice chromosome 12 with the largest BAC contig covering 855 kb. The whole physical map had a size of ∼16 Mb and covered about 52% of rice chromosome 12. This physical map will be certainly helpful for map-based gene cloning of agronomically and biological important genes and understanding the genome structure of the chromosome.

The differential scanning calorimetric (DSC) curves of the mitochondria isolated from two varieties of sporophyte cytoplasmic male sterile and their fertile lines of Yie Bai and Ma Xie type rice have been determined. The curves show that the energy is released continuously as temperature rise to 70°C. Some thermodynamic and kinetic parameters of the energy release of the mitochondria have been obtained. The presented results showed that the mitochondria from cytoplasmic male sterile rice released more heat and they had higher energy barrier, less rate, and more complicated mechanism than that of their fertile lines in the energy release process.

The power-time curves of the germination of different rice and tree seeds have been studied by using a microcalorimeter set up by ourselves. Some characteristic values have been obtained from these curves in different thermogenesising stages of the germination of rice and tree seeds. These parameters can be used in comparison of character and activity for different seeds, moreover the effects of different strain germinating shape and temperature on the power-time curves of the germination of seeds have been discussed.

RNA editing exists extensively in the higher plant mitochondria, and is a required step for forming functional proteins. There may be some relationship between RNA editing and cytoplasmic male sterility (CMS), a kind of phenomenon that is attributed to mitochondrial genome mutations. The research materials used are the gametophytic male sterility line (A), maintainer line (B) and F1 hybrid (F1) of HL-type CMS rice. cDNAs and DNAs of atp6 and coxII have been obtained from A, B and F11 by PCR and RT-PCR. Comparing sequences of cDNAs and DNAs, 18 and 15 editing sites were found respectively in the transcripts of atp6 and coxII. A, B and F1 shared the same editing sites. RNA editing improves hydrophobicity and conservation of the predicted protein as compared with other organisms.