Co-expression of soybean Dicer-like genes in response to stress and development.

Regulation of gene transcription and post-transcriptional processes is critical for proper development, genome integrity, and stress responses in plants. Many genes involved in the key processes of transcriptional and post-transcriptional regulation have been well studied in model diploid organisms. However, gene and genome duplication may alter the function of the genes involved in these processes. To address this question, we assayed the stress-induced transcription patterns of duplicated gene pairs involved in RNAi and DNA methylation processes in the paleopolyploid soybean. Real-time quantitative PCR and Sequenom MassARRAY expression assays were used to profile the relative expression ratios of eight gene pairs across eight different biotic and abiotic stress conditions. The transcriptional responses to stress for genes involved in DNA methylation, RNAi processing, and miRNA processing were compared. The strongest evidence for pairwise co-expression in response to stresses was exhibited by non-paralogous Dicer-like (DCL) genes GmDCL2a-GmDCL3a and GmDCL1b-GmDCL2b, most profoundly in root tissues. Among homoeologous or paralogous DCL genes, the Dicer-like 2 (DCL2) gene pair exhibited the strongest response to stress and most conserved co-expression pattern. This was surprising because the DCL2 duplication event is more ancient than the other DCL duplications. Possible mechanisms that may be driving the DCL2 co-expression are discussed.