Browsing by Author "Ho, Shao-Wei"

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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.
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    石櫟屬物種生理生態性狀親緣訊息與蠟生合成基因正向天擇
    (2016) 何紹瑋; Ho, Shao-Wei
    有些植物表皮細胞中的蠟生合成基因生合成蠟後，經通道蛋白運輸至細胞外堆疊，形成物理性屏障的結晶狀(epicuticular wax crystal)構造，常被認為與化學性防禦特徵(如：酚酸)之間有權衡關係。此外，葉表蠟有無的適應也可能反映在蠟生合成基因及受蠟影響的生態特徵上，如光合作用效率。本研究以石櫟屬物種作為材料，利用遺傳及生理生態分析探討葉表蠟結晶的有/無特徵是否為適應的結果。首先使用6個參考基因重建石櫟屬的親緣關係，發現距今約1400萬年前至800萬年前，至少出現3次獨立由無蠟到產生蠟結晶的特徵轉換的演化事件。在蠟骨架生合成(CER1、CER3)、調節性(CER7)、及運輸蛋白(CER5)等基因中，僅發現CER1在由無蠟到產生蠟結晶的特徵轉換時有正向天擇訊號；生理生態檢測中，蠟結晶均與酚酸及光合作用指數無顯著相關。但Y(II)及δ15N等光合作用指數在CER1基因樹呈現顯著的親緣訊息，顯示光合作用效率在種間的差異反應在蠟骨架合成的演化上。本研究推論，石櫟屬物種在中新世中期至上新世初期發生特徵轉換，當時劇烈的氣候變化也反映了蠟結晶生合成基因的正向天擇及光合作用效率上。