Degeneration of photosynthetic capacity in mixotrophic plants, Chimaphila japonica and Pyrola decorata (Ericaceae)

The evolution of photosynthesis is an important feature of mixotrophic plants.Previous inferences proposed that mixotrophic taxa tend to retain most genes relating to photosynthetic functions but vary in plastid gene content.However,no sequence data are available to test this hypothesis in Ericaceae.To investigate changes in plastid genomes that may result from a transition from autotrophy to mixotrophy,the plastomes of two mixotrophic plants,Pyrola decorata and Chimaphila japonica,were sequenced at Illumina's Genome Analyzer and compared to the published plastome of the autotrophic plant Rhododendron simsii,which also belongs to Ericaceae.The greatest discrepancy between mixotrophic and autotrophic plants was that ndh genes for both P.decorata and C.japonica plastomes have nearly all become pseudogenes.P.decorata and C.japonica also retained all genes directly involved in photosynthesis under strong selection.The calculated rate of nonsynonymous nucleotide substitutions and synonymous substitutions of protein-coding genes(dN/dS) showed that substitution rates in shade plants were apparently higher than those in sunlight plants.The two mixotrophic plastomes were generally very similar to that of non-parasitic plants,although ndh genes were largely pseudogenized.Photosynthesis genes under strong selection were retained in the two mixotrophs,however,with greatly increased substitution rates.Further research is needed to gain a clearer understanding of the evolution of autotrophy and mixotrophy in Ericaceae.

喜冬草的化学成分研究

目的:对喜冬草的化学成分进行研究。方法:采用硅胶柱色谱和Sephadex LH-20凝胶柱色谱等方法进行分离纯化,通过所得单体化合物的理化性质和波谱分析(^(1)H-NMR与^(13)C-NMR)以及相关文献的佐证确定化合物结构。结果:从喜冬草中分离得到10个化合物,分别鉴定为:梅笠草素(1)、α-香树精(2)、3α-羟基-20-烯-乌苏烷(3)、β-谷甾醇(4)、蒲公英萜醇(5)、1-四氢萘酮(6)、熊果醇(7)、triptohypol E(8)、熊果酸(9)、2α,3α,23-三羟基乌苏烷-12-烯-28-酸(10)。结论:其中,化合物2、3、6~8、10为首次从喜冬草属植物中分离得到,化合物2~10为首次从该植物中分离得到。