【作者】 杜颖颖；

【导师】 梁月荣；

【作者基本信息】 浙江大学 ， 茶学， 2009， 博士

【摘要】 新梢白化茶树品种是由一类茶树特殊突变体培育而成的,它们在一定生态环境条件下生长出白化新梢或嫩叶,并具有氨基酸含量高和滋味鲜爽等品质特点,适合生产优质绿茶。新梢白化茶树品种的白化现象受环境条件影响,化学成分含量也随环境条件而产生波动,对品质控制存在困难。针对这些问题,本文通过不同温度和光照处理,研究这类茶树的新梢白化现象,并从基因表达和超微结构以及生物化学成分等方面探讨新梢白化茶树的白化机理;同时采用RAPD技术分析鉴定新梢白化茶树特有DNA分子标记。为新梢白化茶树遗传育种和高产优质栽培技术措施的制定提供科学依据。通过不同温度和夏季强光照条件下遮荫处理,证明目前在中国有两类新梢白化茶树品种,一类是低温诱导型新梢白化茶树,另一类是强光诱导型新梢白化茶树。前者在温度低于20℃时出现新梢白化,温度高于20℃时白化叶片返绿,达到25℃时与一般绿茶品种无异。强光照诱导型新梢白化茶树在高温强光的夏季生长出黄色的白化新梢,当遮光处理时白化叶片返绿。茶叶的化学成分含量与白化程度有关,白化新梢的氨基酸含量高于普通茶树品种,而茶多酚总量低于普通茶树品种,咖啡因含量略低,水浸出物含量与常规品种相当。以福鼎大白茶为对照,采用RAPD技术对“黄金芽”等7个新梢白化茶树品种进行分析,获得21个特异DNA分子标记。特异DNA分子标记经测序,其中S17.10、S28.15、S31.15和S36.08等4个标记的DNA序列明确,可转化为STS或SCAR的分子标记应用于相应新梢白化茶树品种的遗传鉴定。以低温诱导型新梢白化茶树品种“小雪芽”为对象研究表明,低温抑制叶片白色体向叶绿体发育,白色体内无类囊体和基粒的堆叠,从而影响叶绿素和类胡萝卜素等色素的生物合成,进而导致叶片白化。在15℃低温条件下,叶片中编码光合作用体系相关基因(lhcb,psbA,RCA等)和类胡萝卜素生物合成相关基因(TOX,VDE)表达下调,而编码质体早期发育阶段的基因accD和编码Cytb6蛋白的petB基因则强烈表达,另一个编码质体转录阶段的基因rrn16s和编码光合作用RuBPCase小亚基基因rbcS等基因表达则不受温度变化的影响。说明低温条件不影响叶绿体的前质体发育,而是抑制从前质体向叶绿体的发育过程,使叶绿体发育不完全,叶绿素等光合作用色素生物合成受阻碍,进而产生叶片白化。以强光照诱导型新梢白化茶树研究表明,与遮光处理相比,在强光照下叶片光合作用体系相关基因psbA、psaB、RCA、rbcL和叶黄素合成相关基因VDE表达下调,而编码质体转录阶段、与脂质合成相关的基因accD表达上调;而且叶绿体发育异常,叶绿体膜和类囊体膜系统发育不完全;光合作用色素叶绿素和参与光淬灭的叶黄素含量降低。证明强光照抑制光淬灭色素叶黄素的生物合成,使叶片容易受到光损伤,叶绿体发育受阻,叶绿素代谢失衡,产生白化,而且光合系统受损。更多还原

【Abstract】 Albino tea cultivars are a group of special tea sultivars and they grow albino or white leaves under special environmental conditions.The albino lea leaves have high concentration of amino acids,which has a special umami taste and is quality materials for processing quality green tea.The albinism and chemical compositions of the leaves on the albino tea cultivars varied greatly with environmental conditions, leading to the difficult in quality control.Gene expressions,leaf ultra-structures, specific DNA markers and chemical compositions of the albino tea cultivars were investigated under different temperature and illumination conditions so as to understand their albino mechanisms.The present studies revealed that there were two kinds of albino tea plants,i.e., low-temperature-induced cultivar and strong light-induced albino tea cultivar.The former grew albino tea shoots when environmental temperature was below 20℃.As the temperature increased to 20℃or above,the albino tea leaf became green.When the temperature reached 25℃,the albino tea cultivars had green leaves as conman as green tea cultivars.The strong light-induced albino tea cultivar grew albino leaves in yellow colour under strong sunlight and high temperature conditions during summer season.The albino leaves became green in colour under shading condition.Chemical compositions of the albino tea shoots varied with the degree of albinism.The albino tea shoots had higher concentration of amino acids,but lower concentrations of tea polyphenols and caffeine than green shoots.The water extractable solids concentration was the same as common green tea cultivars.Seven albino tea cultivars and one common green tea cultivar(’Fudingdabai’,as control) were used to investigate specific DNA marker using RAPD method and 21 specific RAPD markers were obtained,among which four(S17.10、S28.15、S31.15 and S36.08) were sequenced and could be used to identify the related albino tea cultivars and to further investigate albinism of the tea cultivars.Low temperature such as 15℃inhibited the chloroplast development from etioplast in the low-temperature-induced albino tea cultivars.At 15℃,the etioplast had no thylakoids and granule stacks,in which biosynthesis of chlorophylls and carotenoids was suppressed,leading to the leaf albinism.Gene expression test revealed that at 15℃,the expressions of genes related to photosynthesis(lhcb,psbA, RCA) and carotenoids biosynthesis(TOX、VDE) in the albino tea cultivar were suppressed while those of genes relating to plastid transcription(accD) and encoding Cytb6 proteine(petB) enhanced greatly.The expressions of gene encoding RuBPCase subunit(rbcS) and gene rrn16s related to the early plastid development were not influenced by the temperature.The results suggested that the development of chloroplast precursor etioplast was not inhibited by low temperature.However,low temperature supressed the development of chloroplast from etioplast,resulting in ateliosis of chloroplast and inhibition of biosynthesis of chlorophylls and carotenoids and finally leaf albinism.The investigation on the strong sunlight-induced albino tea cultivar "Huangjinya" showed that,compared to sunlight shading condition,the expressions of genes psbA、psaB、RCA、rbcL which relate to photosynthesis apparatus and gene VDE relating to biosynthesis of xanthin were down regulated,while gene accD which relates to the plastid transcription and lipid biosynthesis was up regulated under strong sunlight condition.The ateliosis of chloroplast membrane and thylakoid membrane was observed under strong sunlight condition,which resulted in suppression of chlorophylls and xanthin.The study confirmed that the biosynthesis of pigments relating to sunlight quenching such as xanthin in the strong sunlight-induced albino tea cultivar was inhibited by strong sunlight,resulting in damage of chloroplast by strong sunlight and suppression of chlorophyll biosynthesis and finally leaf albinism.更多还原