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布莱顿大学排名:植物克隆CCD亞基因家族研究綜述

來源:原創論文網 添加時間:2019-04-11

布莱顿西服 www.ybzmtt.com.cn   摘    要: 類胡蘿卜素是植物中一類重要的色素群, 經類胡蘿卜素裂解雙加氧酶 (carotenoid cleavage dixoygenases, CCDs) 或非酶作用合成的阿樸類胡蘿卜素及其衍生物在植物中可以作為著色劑、植物激素、芳香物質和信號物質。CCD基因家族包括CCD和NCED兩個亞家族。到目前為止, 植物中克隆得到的CCD亞基因家族成員有5個, 包括CCD1、CCD2、CCD4、CCD7和CCD8;其中CCD1和CCD4參與了多種植物花、果實的著色及其香氣物質 (如α-紫羅酮、β-紫羅酮) 的形成;CCD2僅在藏紅花屬 (Crocus) 植物中發現, 參與藏紅花屬植物的花香和花色物質 (如藏花酸) 的形成;CCD7和CCD8參與激素獨腳金內酯的合成。本文概述了高等植物中各類CCD亞家族基因成員的結構、表達特性和功能等, 并展望了進一步的研究方向和重點, 以期為該基因家族功能研究和今后的應用提供參考。

  關鍵詞: 類胡蘿卜素裂解雙加氧酶 (CCD) ; 類胡蘿卜素降解; 植物激素; 阿樸類胡蘿卜素;

  Abstract: Carotenoids are one of the most important pigments in plants, apocarotenoids from carotenoids via carotenoids cleavage dioxygenases (CCDs) or non-enzyme pathway and their derivatives play an important role in plants as pigment, plant hormone, volatiles and signals. CCD family consists of two subfamilies: CCD and NCED. To date, five members in CCD subfamily including CCD1, CCD2, CCD4, CCD7 and CCD8 have been cloned from higher plants. It has been proved that CCD1 and CCD4 play important role in color and volatiles (eg, α-ionone and β-ionone) formation of flowers and fruits in plants. CCD2 was only found in Crocus plants, which was involved in the formation of aroma and pigments (eg, crocetin) . CCD7 and CCD8 were involved in formation of strigolactone. In this paper, in order to provide references for the functional research and future application of CCD subfamily genes, the structure, expression patterns and functions of various members of CCD subfamily genes in higher plants are summarized, and further research directions and keynote are prospected.

  Keyword: Carotenoid cleavage dixoygenases (CCD) ; Carotenoid degradation; Plant hormone; Apocarotenoid;

  類胡蘿卜素是廣泛分布于自然界中的一類色素, 迄今已發現近800種天然類胡蘿卜素 (Johnson, 2009) , 是眾多植物果實如:枸杞 (Lycium chinense) (Tian et al., 2015) 、溫州蜜柑 (Citrus unshiu) (Kato et al., 2006) 、番茄 (Lycopersicon esculentum) (Simkin et al., 2004a) 和花如:杜鵑 (Rhododendron japonicum) (Ureshino et al., 2016) 、菊花 (Chrysanthemum morifolium) (Yoshioka et al., 2012) 、桂花 (Osmanthus fragrans) (Han et al., 2014) 的重要呈色物質。同時, 類胡蘿卜素可以作為合成多種具有生物活性物質的前體, 類胡蘿卜素經過氧合酶或非酶裂解作用可以形成阿樸類胡蘿卜素 (Hou et al., 2016) ;而阿樸類胡蘿卜素及其衍生物可以作為著色劑、香氣物質以及調節因子和信號物質等, 在吸引傳播媒介 (昆蟲、鳥類等) 傳播花粉和種子以及調控植物生長發育等方面起重要作用 (Cazzonelli, Pogson, 2010) 。其中, 類胡蘿卜素裂解雙加氧酶 (carotenoid cleavage dixoygenases, CCDs) 是這些類胡蘿卜素裂解氧合酶 (carotenoid cleavage oxygenases, CCOs) 中重要的一支, 參與了植物中多種類胡蘿卜素的降解形成β-紫羅酮、α-紫羅酮和獨腳金內酯 (strigolactone, SL) (Auldridge et al., 2006b) 。
 

植物克隆CCD亞基因家族研究綜述
 

  CCD家族是植物中相對較小的基因家族, 包括CCD和9-順式-環氧類胡蘿卜素雙加氧酶基因 (nineepoxycarotenoid dioxygenase, NCED) 兩個亞家族 (Ohmiya, 2009) 。第一個被發現的CCD基因家族成員是Schwartz等 (1997) 在玉米 (Zea mays) 中分離獲得的屬于NCED亞家族的VP14。目前在植物中發現的CCD家族成員共有12個, 其中CCD亞家族有5個 (CCD1, CCD2, CCD4, CCD7和CCD8) ;NCED亞家族7個 (NCED1, NCED2, NCED3, NCED4, NCED5, NCED6和NCED9) 。在擬南芥 (Arabidopsis thaliana) 中, CCD家族共有9個成員, CCD亞家族4個 (CCD1, CCD4, CCD7和CCD8) , NCED亞家族5個 (NCED2, NCED3, NCED5, NCED6, NCED9) (Auldridge et al., 2006a) 。在其他植物中發現的類似基因則根據該基因與擬南芥中CCD基因的親緣關系和同源性來命名。Walter和Strack (2011) 根據CCD基因家族成員的裂解位點和作用底物的差異性將其分為5個亞家族:CCD1、CCD4、CCD7、CCD8和NCED。但基于基因的同源性、底物特異性以及酶活性差異 (Ohmiya, 2009) , 本文將其分為兩個亞家族, 并著重介紹CCD亞家族的研究進展。

  1 CCD1基因

  1.1 CCD1基因結構

  根據起始密碼子位置差異, 部分物種中CCD1基因分為兩類:CCD1a和CCD1b, 如玉米 (Sun et al., 2008) 、番茄 (Wei et al., 2015) 、藏紅花 (Crocus sativus) (Rubio et al., 2008) , 而其他的物種則只有一種CCD1, 如草莓 (Fragaria×ananassa) (Carmen et al., 2008) 。CCD1基因ORF為1 620 bp左右, 其翻譯的氨基酸序列長度為540 aa左右 (表1) 。葡萄 (Vitis vinifera) 中VvCCD1基因ORF長度為1629 bp (Mathieu et al., 2005) , 玉米中ZmCCD1基因ORF長度為1 623 bp (Sun et al., 2008) 。從其內含子數目看, 水稻 (Oryza sativa) 和擬南芥CCD1基因分別含有11和13個內含子 (Auldridge et al., 2006b) 。

  1.2 CCD1蛋白的作用位點和裂解底物

  CCD1在不同植物中裂解的底物、作用位點都不盡相同, 較為普遍的的裂解位點是9, 10 (9'~10') 碳雙鍵。例如青蒿 (Artemisia annua) (Liu et al., 2011) 、玉米 (Sun et al., 2008) 、桂花 (Baldermann et al., 2010) 和溫州蜜柑 (Kato et al., 2006) 的CCD1重組蛋白都能裂解β-隱黃質、玉米黃質、以及全反式紫黃質的9, 10和9', 10'位置, 以及9-順式紫黃質的9, 10位置從而形成β-紫羅蘭酮 (β-ionone) 、β-環檸檬醛 (β-cyclocitral) 、香葉基丙酮 (geranylacetone) 和假紫羅蘭酮 (pseudoionone) 等芳香類物質。而突厥薔薇 (Rosa damascena) 的RdCCD1 (Huang et al., 2009a) 、厚皮香瓜 (Cucumis melo) 的CmCCD1 (Ibdah et al., 2006) 、番茄的SlCCD1B (Ilg et al., 2014) 、月桂 (Laurus nobilis) 的LnCCD1 (Yahyaa et al., 2015) 可裂解多種順式和全反式類胡蘿卜素以及不同的阿樸類胡蘿卜素生成α-紫羅酮、β-紫羅酮等多種芳香性物質以及6-甲基-5-庚烯-2-酮和香葉醛 (Ilg et al., 2009) 。6-甲基-5-庚烯-2-酮是玉米中的重要揮發性物質, 在番茄紅素的裂解位點是5, 6 (5', 6') 碳雙鍵。體外分析中, ZmCCD1裂解線性和環化的類胡蘿卜素的效率是相當的。根據阿樸類胡蘿卜素揮發性物質的合成模式分析, 有學者認為CCD1是根據碳7和8 (7', 8') 、碳11和12 (11', 12') 之間的飽和狀態或在碳5、9和13 (5', 9', 13') 上的甲基集團來識別它的裂解位點 (Vogel et al., 2008) 。有的物種, 如胡蘿卜 (Daucus carota) 的DcCCD1, 不能裂解線性胡蘿卜素 (Yahyaa et al., 2013) 。例如在水稻中的體內分析表明OsCCD1的作用底物是阿樸類胡蘿卜素 (Ilg et al., 2010) 。因為CCD1編碼的蛋白并不定位于質體上 (Auldridge et al., 2006a) , 故而在植物體內只能利用由CCD其他家族成員裂解的阿樸類胡蘿卜素為底物 (Hou et al., 2016) (表2) 。

  表1 植物CCD亞家族基因結構
表1 植物CCD亞家族基因結構

  -:相關信息參考文獻中未提及

  -:Related information was not mentioned in reference

  1.3 CCD1表達特性

  CCD1表達的部位主要有花瓣 (Baldermann et al., 2012) 、葉片 (Lashbrooke et al., 2013) 、果實 (Tian et al., 2015) 和柱頭 (Rubio et al., 2008) , 在柑橘屬 (Citrus) 的物種中, CitCCD1則主要在橘皮和汁囊中表達 (Kato et al., 2006) 。有些物種CCD1則是組成型表達, 如藏紅花 (Crocus sativus) 的CsCCD1a (Rubio et al., 2008) 。從表達時期上看, 葡萄的VvCCD1在轉色期之前表達量開始升高, 成熟過程中則趨于穩定 (Mathieu et al., 2005) 。類似的, 胡蘿卜的DcCCD1 (Yahyaa et al., 2013) 、歐洲越橘 (Vaccinium myrtillus) 的VmCCD1 (Karppinen et al., 2016) 、香瓜的CmCCD1 (Ibdah et al., 2006) 和草莓的FaCCD1 (Carmen et al., 2008) 在根和果實成熟過程中其表達都會上調 (表3) 。

  目前的結果表明CCD1的表達主要受光照、晝夜節律、不同光質、激素、NaCl以及高溫處理等物理因素和真菌侵染等生物因素的影響。桂花OfCCD1 (Baldermann et al., 2010) 的表達受光周期影響, 白天表達量升高而夜間降低;矮牽牛 (Petunia hybrida) PhCCD1 (Simkin et al., 2004b) 的表達會受到光照的影響, 而越桔 (Vaccinium myrtillus) 的VmCCD1 (Karppinen et al., 2016) 在紅光/遠紅光下表達上調。另外, NaCl、干旱、高溫和脫落酸 (abscisic acid, ABA) 處理后堿蓬 (Suaeda salsa) SsCCD1的表達量會升高 (Cao et al., 2005) 。在大豆 (Glycine max) 中, GmCCD1對ABA處理有較強的響應 (Wang et al., 2013) 。另外, 玉米的ZmCCD1在真菌侵染的菌根中表達量會升高 (Sun et al., 2008) 。

  1.4 CCD1的功能

  CCD1酶活蛋白主要作用是裂解類胡蘿卜素生成香氣物質 (Floss, Walter, 2009) 。例如在釀酒酵母 (Saccharomyces cerevisiae) 中同時轉入了crtYB和PhCCD1后, β-紫羅酮的合成增加了8.5倍 (López et al., 2015) 。相反的, 降低矮牽牛PhCCD1的轉錄水平導致β-紫羅酮的合成下降了58%~76% (Simkin et al., 2004b) 。

  2 CCD2基因

  2.1 CCD2基因結構

  CCD2是最近新發現的一個CCD家族的成員, 目前只在藏紅花屬 (Crocus) 的植物中發現 (Ahrazem et al., 2015a) 。最近的研究發現了三類CsCCD2基因, 分別為CsCCD2a、CsCCD2b和CsCCD2-t。其中CsCCD2a含有9個內含子、10個外顯子, CsCCD2b含有8個內含子和9個外顯子, 而CsCCD2-t沒有內含子, 缺少第8外顯子 (Ahrazem et al., 2016) 。CaCCD2的cDNA長2238 bp, 編碼622個氨基酸 (Ahrazem et al., 2015a) (表1) 。

  2.2 CCD2蛋白的作用位點和裂解底物

  CCD2的過表達會使藏紅花的花被片、柱頭呈現黃色、橙色以及紅色 (Ahrazem et al., 2016) 。在藏紅花柱頭中, CsCCD2先后在7-8, 7'-8'碳雙鍵裂解玉米黃質, 經中間產物3'-OH-β-阿樸-8'-胡蘿卜醛最終生成藏花酸二醛 (Frusciante et al., 2014) 。

  2.3 CCD2表達特性

  CsCCD2在藏紅花花柱中表達, 在花柱橙色期達到最大值 (Frusciante et al., 2014) 。CaCCD2則主要在花被和柱頭中表達 (Ahrazem et al., 2015a) 。CsCCD2啟動子中含有光響應以及溫度響應元件, 進一步研究發現黑暗以及低溫處理會誘導CsCCD2表達;光照和高溫抑制CsCCD2的表達 (Ahrazem et al., 2016) (表3) 。

  2.4 CCD2的功能

  CCD2酶活蛋白是藏紅花中藏花酸合成的關鍵酶, 并進一步糖基化生成西紅花苷, 西紅花苷是令藏紅花花柱中的橙色物質。同時也有研究表明, CsCCD2L和CaCCD2與CCD4一樣都定位于質體上的 (Ahrazem et al., 2015a) 。但是, 近來有研究表明在梔子 (Gardenia jasminoides) 中, 參與藏花素合成的最有可能的是CCD4而不是CCD2, 因為在梔子的轉錄組數據中并未發現CCD2 (Ji et al., 2017) (表2) 。

  3 CCD4基因

  3.1 CCD4的基因結構

  柑橘屬 (Citrus) 中根據CCD4保守結構域的差異可以分5個亞支:CitCCD4a、b、c、d和e (Zheng et al., 2015) 。而在菊花中CmCCD4a又可以分為CmCCD4a-1至CmCCD4a-4 (Yoshioka et al., 2012) 。按照有無內含子來分, CCD4亞家族可以分為3類:無內含子、1個內含子和2內含子, 分別以擬南芥的AtCCD4、菊花的CmCCD4和桂花的OfCCD4為代表 (Huang et al., 2009b) 。CCD4的ORF框長度差異性較大, 短的如紅木 (Bixa orellana) 的BoCCD4, 只有1053 bp, 編碼501個氨基酸 (Sankari et al., 2016) , 長的如OfCCD4, 1827 bp, 可編碼609個氨基酸 (Huang et al., 2009b) (表1) 。

  表2 CCD亞家族基因功能
表2 CCD亞家族基因功能
表2 CCD亞家族基因功能
表2 CCD亞家族基因功能

  3.2 CCD4蛋白的作用位點和裂解底物

  菊花CmCCD4和蘋果 (Malus×domestica) MdCCD4在大腸桿菌 (Escherichia coli) 中可以裂解β-胡蘿卜素生成β-紫羅酮 (Huang et al., 2009b) 。在土豆 (Solanum tuberosum) 中StCCD4也可以在9', 10'位置裂解全反式-β胡蘿卜素, 生成β-紫羅酮 (Mark et al., 2015) 。此外, 紅木的BaCCD4a與藏紅花的CsCCD4a親緣關系很近, 這表明該基因也可能參與了香氣形成, 吸引昆蟲以及傳粉等過程 (Sankari et al., 2016) 。在蜜柑 (Citrus unshiu) 的果皮中, CitCCD4能在7, 8/7', 8'碳雙鍵裂解β-隱黃質和玉米黃質, 合成β-橙色素, 但不能裂解其他的類胡蘿卜素 (Ma et al., 2013) (表2) 。

  3.3 CCD4基因的表達特性

  與CCD1的表達特點類似, CCD4主要在雄蕊 (Wei et al., 2015) 、柱頭 (Rubio et al., 2008) 、花 (Tuan et al., 2013) 、葉片 (Lashbrooke et al., 2013) 和果實 (Ma et al., 2013) 等器官和組織中表達, 如葡萄的VvCCD4a和VvCCD4b分別在葉和果實表達量最高 (Lashbrooke.et al., 2013) 。有些幾乎在所有的器官中都表達, 但不同的器官中表達量不同, 如McCCD4, 在花中最高, 嫩葉、莖平穩, 老葉、根中最低 (Tuan et al., 2013) 。有的隨植物發育階段的變化而變化, 如野百合 (Lilium brownii) 的LbCCD4, 花開后12 h表達量達到最高, 并保持高表達量 (Hai et al., 2012) 。有的則是組成成型表達的, 如柑橘CitCCD4a (Zheng et al., 2015) 。CCD4的表達同時也會受到脅迫、光照以及表觀修飾等因素的影響, 不過不同物種有所不同。如乙烯和紅光處理上調CitCCD4的表達 (Ma et al., 2013) , 而傷害、高溫、冷以及滲透脅迫會使藏紅花CsCCD4c表達量升高 (Angela et al., 2014) (表3) 。NaCl、聚乙二醇 (polyethylene glycol, PEG) 、高溫和低溫處理后, 大豆CCD4表達量都呈現先升高后降低的趨勢 (Wang et al., 2013) 。在桂花中, '橙紅丹桂' (Of.'Chenghong Dangui') OfCCD4啟動子CG島甲基化會下調OfCCD4的表達 (Han et al., 2014) 。

  3.4 CCD4基因的功能

  除CCD1外, 目前經過報道的CCD家族的酶都是定位于質體上的。如CCD4, 可以利用質體中的類胡蘿卜素 (Rottet et al., 2016) 。CCD4對類胡蘿卜素的裂解與果肉、花器官的著色有關, 也與香氣物質的合成有關。CCD4a/b四個酶可能都與藏紅花中β-紫羅酮的形成有關 (Rubio et al., 2008) 。近來有研究表明, 過表達擬南芥AtCCD4基因的水稻中β-胡蘿卜素和葉黃素明顯降低74%和72%, β-紫羅酮增加了2倍 (Song et al., 2016) 。CCD4功能的正常行使和功能缺失會造成果實、花器官顏色的改變。杜鵑黃色花瓣褪色 (Ureshino et al., 2016) 、桃 (Prunus persica) 果肉呈現白色 (Adami et al., 2013) 、洋桔梗 (Eustoma grandiflorum) (Liu et al., 2013) 淺黃色和白色花的形成以及百合 (Hai et al., 2012) 花被片由黃變白等表型的改變和形成是由CCD4裂解類胡蘿卜素造成的。同時, CCD4表達的差異也是造成不同桂花品種花色的關鍵因素 (Wang et al., 2018) 。相反的, 桃子 (Fukamatsu et al., 2013) 果肉呈現黃色、油菜 (Brassica napus) (Zhang et al., 2015) 和菊花 (Jo et al., 2016) 花色由白變黃, 則是CCD4失活進而導致類胡蘿卜素的含量增加造成的 (Adami et al., 2013;Bai et al., 2015) 。CCD4是擬南芥種子類胡蘿卜素積累的負調控因子, CCD4功能缺失可以使其β-胡蘿卜素的含量增加了8.4倍 (Sabrina et al., 2013) 。在西葫蘆 (Cucurbita pepo) 中與類胡蘿卜素降解關系最為密切的同樣是CCD4 (GonzalezVeldejo et al., 2015) 。這些證據表明, 在桂花、杜鵑和百合等植物中, CCD4是控制它們花色呈現的關鍵基因。并且已經有報道通過病毒介導沉默桃白色果肉桃中的CCD4后, 基因沉默株系的果肉變黃 (Bai et al., 2015) 。這說明通過基因沉默等技術控制CCD4的表達進而創造不同花色的觀賞植物是可行的。

  4 CCD7和CCD8基因

  4.1 CCD7和CCD8基因的結構特點

  CCD7按其外顯子數目可以分為兩類, 第一類含有6個外顯子, 如藏紅花CsCCD7 (Rubiomoraga et al., 2014) , 第二類含有7個外顯子, 如番茄的SlCCD7 (Vogel et al., 2009) 。CCD8根據外顯子數量可分為三類, 第一類只有3個外顯子, 如玉米的ZmCCD8;第二類有5個外顯子, 如水稻的OsCCD8 (Rubiomoraga et al., 2014) ;第三類有6個外顯子, 如土豆的StCCD8 (Pasare et al., 2013) (表1) 。

  4.2 CCD7和CCD8蛋白的作用位點和裂解底物

  獨腳金內酯能抑制植物側枝萌發, 并且主要在根內合成 (Mikihisa et al., 2008) 。首先, 全反式β-胡蘿卜素在β-胡蘿卜素順-反異構酶Dwarf27 (β-carotene cis-trans isomerase Dwarf27, D27) 的作用下生成9-順式-β-胡蘿卜素, 隨后CCD7裂解9-順式-β-胡蘿卜素的9'~10'位碳雙鍵生成9-順式-β-阿樸-10'-胡蘿卜醛 (Alder et al., 2012) 。在CCD8的作用下將9-順式-β-阿樸-10'-胡蘿卜醛轉變成己內酯 (carlactone) (Bruno et al., 2017) 。己內酯轉變為獨腳金內酯的機理尚不完全清楚, 在水稻 (Zhang et al., 2014) 和擬南芥 (Booker et al., 2005) 中的研究表明由MAX1編碼的細胞色素酶P450與該過程有關。而CCD7和CCD8還參與了另一條代謝通路, 在積累全反式-β-胡蘿卜素的大腸桿菌中, AtCCD7和AtCCD8能先后裂解全反式-β-胡蘿卜素的9, 10和13, 14碳雙鍵, 生成C18的酮 (β-apo-13-carotenone) (Schwartz et al., 2004) 。不過該酮的結構與獨腳金內酯相差甚遠, 并且用其處理水稻ccd8突變體后, 并未形成與野生型類似的表型 (Alder et al., 2012) (表2) 。

  表3 植物CCD亞家族基因表達特點
表3 植物CCD亞家族基因表達特點
表3 植物CCD亞家族基因表達特點
表3 植物CCD亞家族基因表達特點

  4.3 CCD7和CCD8的表達特性

  CCD7在不同物種中表達特點類似, 在番茄中SlCCD7在所有組織中均有表達, 在黃色果實中表達量最高 (Wei et al., 2015) , 同樣的, 藏紅花CsCCD7在所有的組織中也均有表達 (Rubiomoraga et al., 2014) 。玉米的ZmCCD7在根、莖、葉、穗中都表達, 根中最高 (Pan et al., 2016) 。番茄SlCCD8 (Wei et al., 2015) 在所有的組織器官中都有表達, 在根中表達量最高, 其次是莖和老葉。獼猴桃 (Actinidia chinensis) AcCCD8 (Ledger et al., 2010) 則主要在根中表達, 在果實發育早期以及種子中表達量相對較低。類似的, 甘蔗 (Saccharum officinarum) ScCCD8在根尖、分蘗芽、腋芽、莖尖等幼嫩組織以及根中高表達, 而在老葉、節和葉鞘中表達量較低 (吳轉娣等, 2016) (表3) 。同時CCD7和CCD8的表達也會受到不同脅迫的影響。如ZmCCD7 (Pan et al., 2016) 和NtCCD8 (Gao et al., 2018) 在缺磷時會上調表達。有研究表明ABA處理下大豆中CCD7和CCD8的表達量都上調 (Wang et al., 2013) 。

  4.4 CCD7和CCD8基因的功能

  CCD7和CCD8是獨腳金內酯合成途徑中的兩個關鍵基因 (Mikihisa et al., 2008) 。CCD7和CCD8某個基因或兩個基因的表達差異會通過影響獨腳金內酯的合成進而影響植物的發育。在百脈根 (Lotus japonicus) 中沉默了LjCCD7的表達后, 與對照組相比, 基因沉默株系有更多側枝和側根, 其總生物量也增加了。同時該株系擁有更長的初級根, 并且其衰老速度被明顯延緩了 (Liu et al., 2013) 。類似的, 在矮牽牛 (Snowden et al., 2005) 、獼猴桃 (Ledger et al., 2010) 、土豆 (Pasare et al., 2013) 、番茄 (Vogel et al., 2009) 和水稻 (Kulkarni et al., 2014) 等多種植物中CCD7和 (或) CCD8參與調控衰老、根的生長、分枝分蘗和花的發育等多種生命活動。近來, 利用CRISPR/Cas9敲除煙草的CCD8后, 結果發現CRISPR/Cas9介導的ccd8突變體煙草有更多的側根和側枝 (Gao et al., 2018) , 這與利用RNAi技術產生的基因沉默植株所產生的表型類似。

  5 總結與展望

  在類胡蘿卜素代謝過程中, CCD亞家族各成員編碼的酶發揮了重要的作用。其主要功能如下: (1) 參與香氣物質的形成和色彩呈現, 在富含類胡蘿卜素的花、塊莖和果肉等組織中, 類胡蘿卜素含量的多少與顏色的深淺有直接關系, 而CCD4和CCD1參與了類胡蘿卜素的降解, 會造成類胡蘿卜素含量變化, 進而早成顏色深淺的改變, 同時裂解產物如α-紫羅酮和β-紫羅酮等使該組織呈現獨特的風味, 如桂花等花卉; (2) 參與特殊成分的合成, CCD2為藏紅花屬植物中所獨有, 并參與藏花酸、藏花醛等物質的合成, 是造成藏紅花屬植物特殊風味與花色的關鍵酶; (3) 參與植物激素的合成, CCD7和CCD8是獨腳金內酯合成通路中的關鍵酶, CCD7和CCD8通過調控獨腳金內酯合成進而調控植物側枝與側根的發育。

  現階段CCD亞家族基因的研究主要集中在基因表達模式、酶的作用底物、裂解位點以及裂解產物等。同時, 關于CCD亞家族的研究也有不甚清楚的地方。例如, 近來研究中發現的參與調控植物生長發育并響應各種脅迫的阿樸類胡蘿卜素信號物質 (apocarotenoid signals, ACSs) , ACS1 (Avenda?o-Vázquez et al., 2014) 。但并未成功分離這些ACSs, 其合成途徑也不清楚。并且, 關于CCD基因亞家族啟動子和轉錄因子的研究仍較少。在今后, 關于CCD亞家族的研究可能會包括: (1) CCD亞家族基因的克隆、功能驗證; (2) CCD亞家族基因啟動子研究; (3) CCD家族基因表達密切相關的轉錄因子的研究; (4) CCD參與的新型植物生長調節物質合成途徑的研究。這些研究的開展有利于更加了解CCD基因家族的作用和分子機理; (5) 利用CRISPR/Cas9和RNAi等技術通過控制CCD家族基因表達, 進而改變植物花色、株型等性狀。

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