Summary
Tropical plants have adapted to strong solar ultraviolet (UV) radiation. Here we compare molecular responses of two tropical mangroves
Avecennia marina
and
Rhizophora apiculata
to high-dose UV-B. Whole-genome bisulfate sequencing indicates that high UV-B induced comparable hyper- or hypo-methylation in three sequence contexts (CG, CHG, and CHH, where H refers to A, T, or C) in
A. marina
but mainly CHG hypomethylation in
R. apiculata
. RNA and small RNA sequencing reveals UV-B induced relaxation of transposable element (TE) silencing together with up-regulation of TE-adjacent genes in
R. apiculata
but not in
A. marina
. Despite conserved upregulation of flavonoid biosynthesis and downregulation of photosynthesis genes caused by high UV-B,
A. marina
specifically upregulated ABC transporter and ubiquinone biosynthesis genes that are known to be protective against UV-B-induced damage. Our results point to divergent responses underlying plant UV-B adaptation at both the epigenetic and transcriptional level.
Due to extensive pleiotropy, trans-acting elements are often thought to be evolutionarily constrained. While the impact of trans-acting elements in gene expression evolution has been extensively studied, relatively little is understood about the contribution of a single trans regulator to interspecific expression and phenotypic divergence. Here, we disentangle the effects of genomic context and miR-983, an adaptively evolving young microRNA (miRNA), on expression divergence between Drosophila melanogaster and D. simulans. We show miR-983 effects promote interspecific expression divergence in testis despite its antagonism with the often-predominant context effects. Single-cyst RNA-seq reveals that distinct sets of genes gain and lose miR-983 influence under disruptive or diversifying selection at different stages of spermatogenesis, potentially helping minimize antagonistic pleiotropy. At the round spermatid stage, the effects of miR-983 are weak and distributed, coincident with the transcriptome undergoing drastic expression changes. Knocking out miR-983 causes reduced sperm length with increased within-individual variation in D. melanogaster but not in D. simulans, and the D. melanogaster knockout also exhibits compromised sperm defense ability. Our results provide empirical evidence for the resolution of antagonistic pleiotropy, and also have broad implications for the function and evolution of new trans regulators.
We investigated plating using fluorine-based rubber, which is a difficult-to-plate material. Adhesion strength of higher than 1.0 kN/m can be achieved using atmospheric UV irradiation for 3 min, followed by heat treatment at 120 ℃ for 60 min.
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