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Title: The atypical genesis and bioavailability of the plant-based small RNA MIR2911: Bulking up while breaking down

Author
item YANG, JIAN - Baylor College Of Medicine
item KONGCHAN, NATEE - Baylor College Of Medicine
item PRIMO PLANTA, CECILIA - Baylor College Of Medicine
item NEILSON, JOEL - Baylor College Of Medicine
item HIRSCHI, KENDAL - Baylor College Of Medicine

Submitted to: Molecular Nutrition and Food Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2017
Publication Date: 3/20/2017
Citation: Yang, J., Kongchan, N., Primo Planta, C., Neilson, J.R., Hirschi, K.D. 2017. The atypical genesis and bioavailability of the plant-based small RNA MIR2911: Bulking up while breaking down. Molecular Nutrition and Food Research. doi:10.1002/mnfr.201600974.

Interpretive Summary: Is it possible that some plant-foods are more nutritious when they are not fresh? To date, health promoting plant bioactive compounds have been shown to decrease after a plant is harvested. Plant based small RNAs are an emerging class of plant bioactive compounds. However, the field of dietary RNAs has suffered from conflicting reports regarding the measurement of plant based small RNAs in circulation. The majority of researchers are unable to detect plant-based microRNAs (miRNAs) in the body fluid of consumers. However, a small RNA of the same size can be detected. Here we document that the bioavailability of this detectable plant small RNA is amplified as the plant food degrades. This is different than the non-detectable miRNAs which are lost during plant degradation. To our knowledge, this represents the first time a bioactive compound increases while the food loses freshness. Future work will now address how this small RNA is amplified an how this observation can be used to improve the nutritional quality of fruits and vegetables as they age.

Technical Abstract: The uptake of dietary plant small RNAs (sRNAs) in consumers remains controversial, which is mainly due to low dietary content in combination with poor fractional absorption. MIR2911, among all the plant sRNAs including microRNAs, has been shown to be one of the most robustly absorbed sRNAs. Here we analyze the unusual abundance and unique genesis of MIR2911 during vegetable processing. Using qRT-PCR, the abundance of MIR2911 increased dramatically in macerated tissues while other microRNAs degraded. The accumulation of MIR2911 correlated with the degradation of the rRNAs, consistent with MIR2911 being derived from the 26S rRNA. Bioinformatic analysis predicts a microRNA-like precursor structure for MIR2911; however, no reciprocal increase in the putative star-strand was noted, and using an Arabidopsis mutation deficient in miRNA processing the accumulation of MIR2911 appeared Dicer independent. MIR2911 was incorporated into the mammalian RNA-induced silencing complex as demonstrated in HEK293T cells, where transfected synthetic MIR2911 modestly suppressed the activity of a cognate luciferase reporter. In conclusion, the genesis and increase of MIR2911 post-harvest is atypical, as traditional plant bioactives are less plentiful as vegetables lose freshness. These findings explain the disparity in serum detection between MIR2911 and canonical plant-based miRNAs.