Transcriptome analysis identifies differentially expressed genes involved in the metabolic regulatory network of progenies from the cross of low phytic acid GmMIPS1 and GmIPK1 soybean mutants
Abstract Lowering the phytic acid (PA) content of crop seeds will be beneficial for improving their nutritional traits. Low phytic acid (lpa) crop lines carrying more than one independent mutated gene have been shown to exhibit more pronounced reductions of PA content than mutants with a single lpa mutated gene. But little is known about the link between PA pathway intermediates and downstream regulation following mutation of these genes in soybean. Here, we performed a comparative transcriptome analysis using an advanced-generation recombinant inbred line [2mlpa (mips1/ipk1)] with low PA and a sibling line with homozygous non-mutant alleles and normal PA [2MWT (MIPS1/IPK1)]. RNA sequencing revealed differential expression levels of numerous genes between seeds of 2mlpa and 2MWT at five developmental stages. A total of 7,945 differentially expressed genes were identified. 3316 DEGs were in 128 metabolic and signal transduction pathways and 4980 DEGs were classified into 345 function terms associated with biological processes. Genes associated with PA metabolism, photosynthesis, starch and sucrose metabolism, and defense mechanisms were related to low PA in 2mlpa soybean line. Among these, 36 genes were up/down-regulated in PA metabolic processes, with 22 possibly contributing to the low PA phenotype of 2mlpa. Most of the genes (81 of 117) associated with photosynthesis were down-regulated in 2mlpa at the late seed stage. Three genes involved in sucrose metabolism were up-regulated at the late seed stage, which might explain the high sucrose content of 2mlpa soybeans. Additionally, 604 genes related to defense mechanisms were differentially expressed between 2mlpa and 2MWT. In this research, the soybean mutant 2mlpa was found to not only exhibit low PA but also have changes in multiple metabolites and secondary metabolites. The results delineate the regulation of these metabolic events by 2mlpa. Many genes associated with PA metabolism would contribute to the drastic reduction of PA and moderate accumulation of InsP3-InsP5 in 2mlpa mutant. And other regulated genes found in photosynthesis, starch and sucrose metabolism, and defense mechanisms would give us more insight into the nutritional and agronomic performance of 2mlpa.