GA_(3)处理对木薯类胡萝卜素生物合成的影响

Effects of GA_(3) Treatment on Carotenoids Biosynthesis in Cassava

木薯(Manihot esculenta Crantz)属大戟科木薯属热带作物,具有耐干旱贫瘠等特性,木薯叶片富含蛋白质,块根富含淀粉但是缺乏类胡萝卜素,是热带低收入人口的主粮。国家木薯产业技术体系"十三五"期间关于木薯产业问题指出,类胡萝卜素是粮饲化的重要指标,类胡萝卜素也是维生素A的前体物质。本文在前期研究中筛选到与类胡萝卜素生物合成相关转录因子MeGAMYB,MeGAMYB是一种受GA响应的转录因子。为了研究其如何介导GA促进类胡萝卜素生物合成的分子机制,明确其与类胡萝卜素含量及其生物合成途径基因的相关关系,本研究用50 mg/L浓度GA_(3)处理培养40 d的‘SC9’茎秆水培苗,在0、3、6、9、12 h取根、茎、叶和叶柄样品检测类胡萝卜生物合成中相关基因的表达情况以及在0、1、2、3、4 d检测类胡萝卜素含量,平行对照用水处理,结果显示:类胡萝卜代谢途径中相关基因以及类胡萝卜素生物合成受GA_(3)诱导,其中叶片在处理4 d时α-胡萝卜素含量最高达到0.19μg/g,是对照的1.2倍;叶片中β-胡萝卜素含量在GA_(3)处理3 d时最高达107.73μg/g,是对照的1.25倍,叶黄素和玉米黄质的含量在处理4 d内都随着GA_(3)处理时间延长含量呈不断增加的趋势。而类胡萝卜素生物合成相关基因如MeLCYB、MeCRTISO、MeZDS、MePDS、MeBCH、MeVDE、MeXAN和MeAAO等和转录因子MeGAMYB的表达量受GA_(3)均上调,其中MeLCYB、MeCRTISO、MePDS、MeBCH、MeAAO和MeXAN等基因的表达趋势与转录因子MeGAMYB的表达趋势一致。本研究可以看出,GA_(3)能促进木薯类胡萝卜素的合成,通过调控类胡萝卜素生物合成相关基因的表达来促进类胡萝卜素的积累,但是具体的调控机制还需要进一步阐释。本结果为研究木薯类胡萝卜素代谢调控机制提供候选功能基因与转录因子,为阐述木薯类胡萝卜素生物合成的机制奠定基础。

Manihot esculenta Crantz (Cassava) is a tropical crop of euphorbiaceae,with the characteristics of drought resistance and infertility.Cassava leaves are rich in protein,and its roots are rich in starch,while poor in carotenoids.Cassava is the staple food of low-income populations in the tropics.The Chinese Cassava Agro-technology System proposed that the content of carotenoids is an important index of cassava diet and feeding during the 13th Five-Year Plan.And carotenoids are also the precursor of vitamin A.A transcription factor MeGAMYB associated with carotenoids biosynthesis was screened out in the previous study,which is a transcription factor responsive to GA.In order to research the molecular mechanism of how MeGAMYB mediateing GA to promote carotenoids biosynthesis in cassava,and to clarify its correlation with carotenoids content and biosynthesis pathway genes,we treated‘SC9’seedlings,which grew up in water culture 40 days with 50 mg/L GA_(3) in present study,and collected the root,stem,leaf,and petiole samples on 0,3,6,9,12 hour to detect the gene expression in the carotenoids biosynthesis pathway,and extracted and detected the content of carotenoids on 0,1,2,3,4 day.The genes involved in the carotenoids metabolic pathway and carotenoids content were both induced by GA_(3).The maximum content ofα-carotene in the leaf was 0.19μg/g with four days treatment,which was1.2 times than that of the control.The maximum content ofβ-carotene in the leaf was107.73μg/g with 3 days GA_(3) treatment,which was 1.25 times higher than that of the control.The content of lutein and zeaxanthin in the leaf increased with the extension of GA_(3) treatment in four days.The expression level of the carotenoids biosynthesis related genes such as MeLCYB,MeCRTISO,MeZDS,MePDS,MeBCH,MeVDE,MeXAN and MeAAO etc.and transcription factor MeGAMYB were all up-regulated in 50 mg/g GA_(3 )treatment.The expression trend of MeLCYB,MeCRTISO,MePDS,MeBCH,MeAAO and MeXAN etc.genes was the same as that of MeGAMYB.The study reveals that GA_(3 )can promote carotenoids biosynthesis in cassava,through regulating the gene expression in carotenoids biosynthesis to promote the accumulation of carotenoids content.While the specific regulatory mechanism needs further explanation.The results would provide candidate genes and transcription factors MeGAMYB for studying carotenoids metabolic regulation mechanisms in cassava.Our research would lay a foundation for elucidating the mechanism of carotenoids biosynthesis in cassava.