A meta-analysis of potential candidate genes associated with salinity stress tolerance in rice

Even though cultivated rice is highly sensitive to salinity, significant variability exists in the primary and secondary gene-pool of rice with respect to traits of salinity tolerance. Breeding salinity tolerance rice varieties is imperative due to climate change and increasing rice demand for global population. A meta-analysis of plethora of genomic data and published literature available on various genes/factors associated with response to rice salinity and tolerance can be used to enlist selected candidates genes affecting salinity. Such genes can be utilized to identify potential candidate salinity resistance genes from donor rice genotypes and facilitate their transfer to high yielding varieties of rice through marker-assisted breeding. This approach has tremendous advantage over transgenic approach as no bio-safety or regulatory issues are involved in exploiting the variability.

Meta-analyses were performed on three datasets viz., rice microarray data of 166 series comprising of 2586 samples, 1228 published research literature in the last one and half decades and RNA-Seq data of 454 and Illumina from Sequence Retrieval Archive (SRA) at NCBI. Among microarray dataset, six salinity related series were finally selected and multi experiment analysis revealed 2289 differentially expressed genes belonging to 44 gene families. Out of these, 13 families viz., AP2-EREBP, AUX/IAA, bZIP, C2H2, bHLH, C3H, HB, HSF, MYB, MYB-related, NAC, Tify and WRKY were selected. Applying various parameters on the published literature data, 13 genes were selected, of which five were common to the different microarray datasets. From RNA-Seq data, total of 751 differentially expressed genes were obtained from 21 gene families, out of which 11 genes were common with those obtained from microarray data and five genes, viz., AP2-EREBP/DREB, MYB, HSF, bZIP and NAC were common to all the three data sets. Based on the results obtained, a total of 31 meta-analyzed genes have been selected and recommended for use in genetic improvement programs aimed at salinity resistance in rice.

The meta-analysis of microarray, RNA-Seq and published literature has been successfully used to select 31 best salinity tolerance associated genes which can be exploited by candidate gene approach for targeted introgression through marker assisted breeding. This approach has multi-fold advantages, as it obviates statutory and ecological issues. Such endeavors are more warranted for combating the key abiotic stresses like salinity, whose effects are increasing due to a changing climate.