Browsing by Author "Gao, Jian"

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    Diversifying selection of the anthocyanin biosynthetic downstream gene UFGT accelerates floral diversity of island Scutellaria species
    (2016-09-17) Huang, Bing-Hong; Chen, Yi-Wen; Huang, Chia-Lung; Gao, Jian; Liao, Pei-Chun
    Abstract Background Adaptive divergence, which usually explains rapid diversification within island species, might involve the positive selection of genes. Anthocyanin biosynthetic pathway (ABP) genes are important for floral diversity, and are related to stress resistance and pollination, which could be responsible for species diversification. Previous studies have shown that upstream genes of ABP are subject to selective constraints and have a slow evolutionary rate, while the constraints on downstream genes are lower. Results In this study, we confirmed these earlier observations of heterogeneous evolutionary rate in upstream gene CHS and the downstream gene UFGT, both of which were expressed in Scutellaria sp. inflorescence buds. We found a higher evolutionary rate and positive selection for UFGT. The codons under positive selection corresponded to the diversified regions, and the presence or absence of an α-helix might produce conformation changes in the Rossmann-like fold structure. The significantly high evolutionary rates for UFGT genes in Taiwanese lineages suggested rapid accumulation of amino acid mutations in island species. The results showed positive selection in closely related species and explained the high diversification of floral patterns in these recently diverged species. In contrast, non-synonymous mutation rate decreases in long-term divergent species could reduce mutational load and prevent the accumulation of deleterious mutations. Conclusions Together with the positive selection of transcription factors for ABP genes described in a previous study, these results confirmed that positive selection takes place at a translational level and suggested that the high divergence of ABP genes is related to the floral diversity in island Scutellaria species.
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    Molecular genetic and biochemical evidence for adaptive evolution of leaf abaxial epicuticular wax crystals in the genus Lithocarpus (Fagaceae)
    (2018-09-17) Yang, Chih-Kai; Huang, Bing-Hong; Ho, Shao-Wei; Huang, Meng-Yuan; Wang, Jenn-Che; Gao, Jian; Liao, Pei-Chun
    Abstract Background Leaf epicuticular wax is an important functional trait for physiological regulation and pathogen defense. This study tests how selective pressure may have forced the trait of leaf abaxial epicuticular wax crystals (LAEWC) and whether the presence/absence of LAEWC is associated with other ecophysiological traits. Scanning Electron Microscopy was conducted to check for LAEWC in different Lithocarpus species. Four wax biosynthesis related genes, including two wax backbone genes ECERIFERUM 1 (CER1) and CER3, one regulatory gene CER7 and one transport gene CER5, were cloned and sequenced. Ecophysiological measurements of secondary metabolites, photosynthesis, water usage efficiency, and nutrition indices were also determined. Evolutionary hypotheses of leaf wax character transition associated with the evolution of those ecophysiological traits as well as species evolution were tested by maximum likelihood. Results Eight of 14 studied Lithocarpus species have obvious LAEWC appearing with various types of trichomes. Measurements of ecophysiological traits show no direct correlations with the presence/absence of LAEWC. However, the content of phenolic acids is significantly associated with the gene evolution of the wax biosynthetic backbone gene CER1, which was detected to be positively selected when LAEWC was gained during the late-Miocene-to-Pliocene period. Conclusions Changes of landmass and vegetation type accelerated the diversification of tropical and subtropical forest trees and certain herbivores during the late Miocene. As phenolic acids were long thought to be associated with defense against herbivories, co-occurrence of LAEWC and phenolic acids may suggest that LAEWC might be an adaptive defensive mechanism in Lithocarpus.