Big roles for small RNAs in polyploidy, hybrid vigor, and hybrid incompatibility.
Small RNAs, including microRNAs (miRNAs), small interfering RNAs (siRNAs), and trans-acting siRNAs (ta-siRNAs), mediate gene expression and epigenetic regulation. While siRNAs are highly diverged, miRNAs and ta-siRNAs are generally conserved but many are differentially expressed between related species and in interspecific hybrids and allopolyploids. On one hand, combination of diverged maternal and paternal siRNAs in the same nucleus may exert cis-acting and trans-acting effects on transposable elements (TEs) and TE-associated genes, leading to genomic instability and endosperm and embryo failures, constituting a bottleneck for the evolution of hybrids and polyploids. On the other hand, cis and trans-acting small RNAs induce quantitative and qualitative changes in epigenetic regulation, leading to morphological variation and hybrid vigor in F1 hybrids and stable allopolyploids as well as transgressive phenotypes in the progeny, increasing a potential for adaptive evolution.
Section of Molecular Cell and Developmental Biology, Center for Computational Biology and Bioinformatics, and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA.
Danny W-K
DW
Ng
Jie
J
Lu
Z Jeffrey
ZJ
Chen
D018506:Gene Expression Regulation, Plant; D006823:Hybrid Vigor / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics; D011123:Polyploidy; D018749:RNA, Plant / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics
D035683:MicroRNAs; D018749:RNA, Plant; D034741:RNA, Small Interfering