The Quest for More Tolerant Rice: How High Concentrations of IronAffect Alternative Splicing?

Rice (Oryza sativa L.) is a global staple food crop and an important model organism for plant studies. Recent reports have shown that alternative splicing is affected by many stressful conditions, suggesting its importance for the adaptation to adverse environments. Due to the little information on this subject, this study aimed to explore changes in splicing patterns that occur in response to high iron concentration in nutrient solutions. Here we quantified different kind of junctions and splicing events in the transcriptome of a relatively tolerant rice cultivar BRS Querencia, under iron excess with concentration of 300 mg L-1 Fe+2. Plants kept under standard conditions (control) presented 127,781 different splicing junctions, while stressed plants had 123,682 different junctions. Canonical (98.85% and 98.91%), semi-canonical (0.73% and 0.70%) and non-canonical (0.42% and 0.40%) junctions were found in control and stressed plants, respectively. Intron retention was the most frequent event (44.1% and 47.4%), followed by 3’ splice site (22.6% and 21.9%), exon skipping (18.9% and 17.3%) and alternative 5’ splice site (14.4% and 13.4%) in control and stressed plants, respectively. We also found 25 differentially expressed genes (five up and 20 down regulated) that are related to post-translational modifications. These results represent an important step in the understanding of how plant stress responses occur in an iron tolerant genotype, uncovering novel genes involved in iron stress response.