Deciphering variation of 239 elite japonica rice genomes for whole genome sequences-enabled breeding.

Revealing genomic variation of representative and diverse germplasm is the cornerstone of deploying genomics information into genetic improvement programs of species of agricultural importance. Here we report the re-sequencing of 239 japonica rice elites representing the genetic diversity of japonica germplasm in China, Japan and Korea. A total of 4.8 million SNPs and PAV of 35,634 genes were identified. The elites from Japan and Korea are closely related and relatively less diverse than those from China. A japonica rice pan-genome was constructed, and 35 Mb non-redundant novel sequences were identified, from which 1131 novel genes were predicted. Strong selection signals of genomic regions were detected on most of the chromosomes. The heading date genes Hd1 and Hd3a have been artificially selected during the breeding process. The results from this study lay the foundation for future whole genome sequences-enabled breeding in rice and provide a paradigm for other species.

Identical probes on different high-density oligonucleotide microarrays can produce different measurements of gene expression.

BACKGROUND: There are many potential sources of variability in a microarray experiment. Variation can arise from many aspects of the collection and processing of samples for gene expression analysis. Oligonucleotide-based arrays are thought to minimize one source of variability as identical oligonucleotides are expected to recognize the same transcripts during hybridization. RESULTS: We demonstrate that although the probes on the U133A GeneChip arrays are identical in sequence to probes designed for the U133 Plus 2.0 arrays the values obtained from an experimental hybridization can be quite different. Nearly half of the probesets in common between the two array types can produce slightly different values from the same sample. Nearly 70% of the individual probes in these probesets produced array specific differences. CONCLUSION: The context of the probe may also contribute some bias to the final measured value of gene expression. At a minimum, this should add an extra level of caution when considering the direct comparison of experiments performed in two microarray formats. More importantly, this suggests that it may not be possible to know which value is the most accurate representation of a biological sample when comparing two formats.