Gene expression profiles between submergence rice (Oryza sativa ssp. indica) varieties, tolerant FR13A and sensitive IR39595-503-2-1-2, under submergence stress were identified using differential display reverse transcriptase-polymerase chain reaction (DDRT-PCR). A total of 1428 bands were amplified with 40 pairs of primers, of which 102 were significantly different between the two lines. The differential display ratio was 7.1%. Among 42 differential display bands derived from the submergence tolerant variety, the expression of seven fragments was confirmed by Northern blot analysis. The analysis of their sequences indicated that four of them showed high homology with genes related to a water stress response: genes encoding ATP-binding protein, isocitrate dehydrogenase, NADH dehydrogenase and terminal acetyltransferase, respectively. The remaining three fragments were novel cDNA fragments.

In order to detect the molecular mechanism of heterosis in pigs, an mRNA differential display (DD) technique was performed to investigate the differences in gene expression in the longissimus dorsi muscle tissues from Meishan, Meishan×Large White cross and Large White pigs. Fourteen expressed sequence tags (ESTs), differentially expressed between the hybrid and purebred pigs, were isolated and identified through semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Nucleotide sequence analysis revealed that the 14 ESTs are not homologous to any of the known genes or ESTs. These novel ESTs were then deposited in the GenBank database. Tissue expression profile analysis showed that the ESTs were expressed in most tissues, including heart, spleen, liver, kidney, small intestine, ovary and lung, and this also implied that these genes must be important for the life process. Our results indicate the diversity of differential display of genes between the hybrids and purebreds in the Meishan×Large White cross combination. Results also suggest that heterosis in pigs might be derived from the differential expression of many indispensable genes in specific life phases.

In order to reveal the molecular basis of heterosis, Large White (LW), an introduced European pig breed, and Meishan (MS), a Chinese indigenous pig breed, were selected to hybridize directly and reciprocally in the present experiment. mRNA differential display (DD) technique was performed to identify genes that were differentially expressed in the backfat tissues of hybrids (LW×MS, MS×LW) and purebred (LW×LW, MS×MS) pigs. The ten anchor primers in combination with ten arbitrary primers (100 sets in total) were used and nearly 1500 reproducible bands were observed in polyacrylamide gels. The 40 differentially displayed bands were selected for cloning and sequencing. Thirty-six out of 40 expressed sequence tags (ESTs) proved to be novel and the sequences were submitted to GenBank (accession No. CV507051-CV507087); the other four showed similarity to known genes published in GenBank. Three among 36 novel ESTs were chosen for further identification with semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). The result showed that two ESTs were differentially expressed, and the third showed no obvious difference between hybrids and purebreds. In order to reduce the percentage of false-positive DD, RNA pools of four types of pigs were constructed, by mixing samples from six pigs of the same genotype, and subjected to DD. Stringent annealing temperature was applied and only bands that could be repeated in duplicate PCR were used for further study. The results showed that the expression pattern of these 36 ESTs differed among the four genotypes of pigs, suggesting that the genes corresponding to these differentially expressed ESTs might be related to the heterosis occurring in fat tissue.

mRNA differential display was used to analyse differences of gene expression between cross combinations, EC and CE, and their parental inbreeds, White Plymouth Rock (EE) and Silkies (CC). Three genes specifically expressed and one gene over-expressed in hybrids were found. By cloning, sequencing and BLAST analysis, one specific expression cDNA band was identified as the cytosolic isocitrate dehydrogenase gene, two were new genes of unknown function, and the over-expressed one was a proteosome subunit p112 gene. The results imply that functional and regulatory genes, expressed or over-expressed in chicken hybrids, are related to heterosis of some carcass traits.

We have characterised the changes in preimplantation embryos that occur in the mRNA population during the transition from maternal to zygotic control of embryogenesis. We connected the mRNA differential display method and RT-PCR based method that allows amplification of the whole population of messengers. In the early stages of development we have further characterised the level of individual mRNAs with the help of semiquantitative RT-PCR used with specific primers. This report concerns four of 12 cDNA fragments that appeared to be differentially expressed between the 4- and late 8-cell stages. A transcript corresponding to fragment no. 1/12 appears to be analogous to the maternal mRNA since it is abundant in 1-, 2-, 4- and 8-cell embryos and rapidly decreases in the later stages. A similar pattern of expression was revealed in the transcript corresponding to fragment no. 8/9. A transcript corresponding to fragment no. 20/8 is newly synthesised from the embryonic genome at the late 8-cell stage and its amount rapidly increases during the following stages. This messenger shows a 91.7% identity with mRNA for human S3A ribosomal protein and 92.2% identity with mRNA for Felis domesticus S3A ribosomal protein. A transcript corresponding to fragment no. 8/19 is stage-specific, being newly synthesised from an embryonic genome at the late 8-cell stage and decreasing in the later stages. This messenger shows 86.6% identity with a mouse mRNA for proline-rich protein and 91.6% identity with human mRNA for KIAA-0058 gene. A complex of these molecular markers represents a suitable tool for answering questions concerning the molecular control of major gene activation during bovine embryogenesis.