Abstract

Chen et al. ( Nature Genet. 51: 1549-1558; Oct. 2019) sequenced Ananas comosus var. bracteatus accession CB5, cultivated for its bright pink-to-red colored fruit, and yellow-fleshed A. comosus accession F153, reporting an improved F153 reference assembly while annotating MICRORNA (MIRNA) loci and gene family expressions relevant to lignin and anthocyanin biosynthesis. An independent article (Xiong et al.Sci. Rep. 8: 1947; 2018) reported var. bracteatus MIRNAs but not MIR828, a negative regulator of anthocyanin and polyphenolics biosynthesis by targeting MYB transcription factors associated with UV light- and sugar-signaling in dicots. MIR828 has been reported in gymnosperms, Amborella (sister to flowering plants), and basal monocot orders Liliales, Asparagales, Zingiberales, Arecales, but not in the Poales, a sister order comprising grasses and ~3,000 species of bromeliads including pineapple. Here I show MIR828 exists in pineapple and directs post-transcriptional gene silencing of mRNAs encoding MYB family members with inferred function to regulate the conspicuous red fruit trait in var. bracteatus. MIR828 plesiomorphy (an ancient basal trait) may shed light on monocot apomorphic fruit development, postulated for 21 monocot families with fleshy fruits as due to homoplasy/convergence driven by tropical climate and/or enticements to vertebrate endozoic seed dispersers.

Highlights

  • Chen et al (Nature Genet. 51: 1549–1558; Oct. 2019) sequenced Ananas comosus var. bracteatus accession CB5, cultivated for its bright pink-to-red colored fruit, and yellow-fleshed A. comosus accession F153, reporting an improved F153 reference assembly while annotating MICRORNA (MIRNA) loci and gene family expressions relevant to lignin and anthocyanin biosynthesis

  • An independent article reported var. bracteatus MIRNAs5 but not MIR8286, a negative regulator of anthocyanin and polyphenolics biosynthesis by targeting MYB transcription factors associated with UV light- and sugar-signaling in dicots7,8

  • I show MIR828 exists in pineapple and directs posttranscriptional gene silencing of mRNAs encoding MYB family members with inferred function to regulate the conspicuous red fruit trait in var. bracteatus

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Summary

Introduction

Chen et al (Nature Genet. 51: 1549–1558; Oct. 2019) sequenced Ananas comosus var. bracteatus accession CB5, cultivated for its bright pink-to-red colored fruit, and yellow-fleshed A. comosus accession F153, reporting an improved F153 reference assembly while annotating MICRORNA (MIRNA) loci and gene family expressions relevant to lignin and anthocyanin biosynthesis. In contrast to demonstrated post-transcriptional silencing activity of miR828 on target MYB expressions in F153 leaf samples (Figure 1), analysis of six bracteatus leaf sRNA libraries from an independent study5 did not provide any evidence of target MYB Aco017254.1 mRNA slicing or target phasiRNA accumulations (Extended data: Table S317).

Results
Conclusion

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