赤霉素类【精品-ppt】

1、6.2.1 发现和结构1、发现1926， 日本人黑泽英一发现水稻恶苗病，该病特点是水稻疯长，不堪负重而死，分析原因是水稻上的赤霉菌所分泌的物质引起。1938，薮田贞次郞等分离出该物质的结晶，命名为赤霉素gibberellin GB。1958，麦克米伦等从豆科植物未成熟的种子中提取出GB。1959，确定其化学结构。2000年底，已发现了127种GB。GB 是一种双萜，由4个异戊二烯单位组成，含19或20个C。其基本结构是赤霉素烷，有4个环，由于环上的双键、羟基数目和位置 的不同，形成了多种赤霉素。GB都含有羧酸，所以称赤霉酸(gibberellic acid, GA)。生理活性最强的GB有GA1

2、、GA3、GA4等，其中GA3(赤霉酸)为植物中最常见的GB，市场有售。图图6.136.13 赤赤霉烷环骨架霉烷环骨架和一些活性和一些活性与非活性的与非活性的GAsGAs的化学的化学结构（引自结构（引自李合生，李合生，20022002）图中图中C C1919-GA-GA包括有活性包括有活性GAGA1 1和和GAGA2020，无活性的无活性的GAGA8 8和和GAGA2929； C C2020-GA-GA有活有活性的性的GAGA3737和和无活性的无活性的GAGA2727。 图图6.146.14 由甲瓦龙酸合成由甲瓦龙酸合成GAGA1212的过程（引自潘瑞炽，的过程（引自潘瑞炽，20012001

3、）1）、分布：在植物界中广泛存在在植物中较多分布在生长旺盛的部位，尤其是未成熟的种子和果实中含量最高。2）、存在形式：1)游离态2)结合态：与糖形成糖苷。3）、运输：无极性，可沿导管向上运输，也可沿韧皮部向下运输，运输速度不同植物差异较大：矮生豌豆5cm/h，豌豆2.1mm/h，马铃薯0.42mm/h。1.前体：甲羟戊酸(甲瓦龙酸)2.途径：1)甲羟戊酸内根-贝壳杉烯(质体)此步受季胺化合物如AMO 1618, Cycocel, Phosphon D的抑制。的抑制。2)内根-贝壳杉烯GA12-7-醛(内质网)3)GA12-7-醛各种GB(细胞质) There is also another p

4、athway for GB synthesis (Recent advances in gibberellin biosynthesis, J.Exp.Bot, Vol40:553-363)图图6.14 6.14 由甲瓦龙酸合成由甲瓦龙酸合成GAGA1212的过程（引自潘瑞炽，的过程（引自潘瑞炽，20012001）图图6.156.15 拟南芥拟南芥的的GAGA代代谢（引谢（引自余叔自余叔文，文，19991999） 1.促进茎的伸长生长1)GB对茎伸长的作用对矮生品种效果明显。2)GB促进伸长的机理与CW酸化无关。其原因在于：A.促进细胞分裂，促进细胞从G1期进入S期，并缩短S期。B.促进CW松

5、驰，可能是使CW中的钙进入胞质。C.促进淀粉、糖的水解，促进渗透吸水。3)GB只增加节间长度而不增加节数Figure Relation between stem elongation and GA1 level2GA1 appears to be the gibberellin that promotes stem extension2. 诱导禾谷类种子-淀粉酶的合成，促进萌发1. GB in coleoptile2. gibberellins diffuse to aleurone layer3. aleurone is induced to synthesize and secrete a

6、lpha amylase and other hydrolases into the endosperm 4. starch and other polymers are degraded to small molecules5. solutes are absorbed by scutellum and transported throughout the growing embryo 3. 打破延迟器官的休眠1ppm GB浸泡刚收获的马铃薯切块56min，取出凉干即可播种。4. 生殖生理作用1)代替长日照使长日植物在短日下开花。(如春性天仙子、金光菊)2)代替低温使未春化植物在常温下开花。

7、(如冬油菜、冬性天仙子) 左：对照，未经低温和GB处理中：10ug GA3处理4周，每天1次右：低温处理6周胡萝卜3)克服植物的幼年性，使二年生植物当年开花。(如二年生作物甘蓝、油菜、胡萝卜)4)促进雄花的形成。5)诱导单性结实。(葡萄、梨、杏等)5.防止衰老脱落GB处理花果，可阻止离层的形成，防止脱落。6.2.4 6.2.4 赤霉素的作用机理赤霉素的作用机理 1 1、 赤霉素促进茎伸长的机制赤霉素促进茎伸长的机制 植物茎伸长是与组成茎的细胞数目的增加及细胞伸长有关。所以GA显著促进茎的伸长可能与增加细胞分裂、促使细胞壁松弛和增加细胞渗透吸水有关。主要是GA促进G1期细胞进入S期以及相应缩短了

8、G1期和S期，从而缩短了细胞分裂间期，促进DNA的合成。一种认为：GA是通过降低细胞壁Ca2+的水平来促进细胞的伸长生长。Moll等（1981）报道，用CaCl2处理过的莴苣下胚轴生长变慢，当加入50mol/L GA3后生长速度增快（图6.17）。另一种认为：GA是通过影响细胞壁结构而控制植物伸长生长。即GA通过降低细胞壁内过氧化物酶的活性，来阻止细胞壁硬化，增加细胞壁的伸展性。图图6.176.17 CaClCaCl2 2和和GAGA3 3对莴对莴苣下苣下胚轴胚轴生长生长速度速度的影的影响响2 2 、赤霉素调控基因表达、赤霉素调控基因表达 GA的处理诱导a-淀粉酶的重新合成（GA诱导大麦离体糊

9、粉层细胞内新合成的蛋白质中， -淀粉酶的比例可高达70%），主要是增加细胞的 -淀粉酶总mRNA数量，也即是增加 -淀粉酶基因的转录速率（图6.18）。图图6.186.18 GAGA3 3 处处理时间理时间与大麦与大麦种子糊种子糊粉层粉层 - -淀粉酶淀粉酶mRNAmRNA翻翻译能力译能力的关系的关系4kAQ(csIY4kAQ(csIY4kAQ)dtJZ5lBR)dtJZ5lBR)dtJZ5lBR)dtJZ5mCS-euK#6mCS-euK#6mCS-euK#6mCS-euL!7nDT+fvL!7nDT+fvL!7nDT+fvL!7nDT0gwM$8oEU0gwM$8oEU0gwM$8oEU0

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