赤霉素和细胞分裂素对石蒜鳞茎膨大的调控作用及其生理机制

The effect and the physiological mechanism of gibberellin and cytokinin on the regulation of Lycoris radiata bulb development

石蒜(Lycoris radiata)鳞茎的自然膨大过程很慢,严重制约了其商业生产的发展,外施激素是调控石蒜鳞茎膨大的重要手段。本文利用外施细胞分裂素类似物氯吡脲(CPPU)、赤霉素(GA)合成抑制剂多效唑(PP333)以及GA的方式,探讨GA和细胞分裂素对石蒜鳞茎膨大的调控作用及其生理机制。研究发现外施CPPU和PP333后,内源玉米素核苷(ZR)和GA3含量分别升高和降低,鳞茎中碳水化合物的积累增强,并促进石蒜鳞茎的膨大。另外,外施GA3和PP333能够快速诱导淀粉合成关键酶腺苷二磷酸葡萄糖焦磷酸化酶(AGPase)大小亚基基因LrAGPL1表达下调、LrAGPS1表达上调,而CPPU对淀粉合成相关基因的调控作用较为缓慢,但是CPPU能够快速上调石蒜鳞茎中细胞分裂标志因子CycD基因的表达。以上结果表明, GA3通过负调控石蒜鳞茎中AGPase的转录水平,抑制AGPase活性,从而减缓鳞茎中淀粉积累过程,最终抑制石蒜鳞茎的膨大,而外施GA3合成抑制剂能够解除这种抑制效应;细胞分裂素能够通过加快石蒜鳞茎中细胞分裂进程来加速鳞茎的膨大,而对淀粉合成酶相关基因的表达的调控可能是间接的。

The slow growth of Lycoris radiata bulbs under natural conditions seriously restricts the development of the L.radiata industry,and the application of exogenous hormones is an efficient way to accelerate the bulb enlargement.In our study,a cytokinin analogue 1-(2-chloropyridin-4-yl)-3-phenylurea(CPPU),gibberellin acid(GA),and a GA synthesis inhibitor PP333 were used to regulate the development of L.radiata bulbs.After the application of exogenous CPPU and PP333,endogenous ZR and GA3 contents were increased and decreased,respectively,and the accumulation rate of carbohydrates in the bulbs was increased,which accelerated the enlargement of L.radiata bulbs.In addition,GA and PP333 application could induce a quick reduction and increase of the expression levels of LrAGPL1 and LrAGPS1 genes which encode AGPase subunits,respectively,while CPPU had a relatively slow regulatory effect on the expression of starch synthesis–related genes,however,CPPU could quickly increase the expression of CycD genes which were indicators of the cell division activity.In conclusion,GA could inhibit the activity of AGPase by negatively regulating the transcription level of AGPase in L.radiata bulbs,resulting in a slow starch accumulation and growth in bulbs,and the application of GA synthetic inhibitor can relieve this inhibitory effect.Cytokinin can accelerate the enlargement of bulbs by promoting the cell division process,and the regulatory effect of cytokinin on the expression of starch synthase–related genes may be indirect.