摘要
淀粉是玉米种子的主要组成成分,它包括直链淀粉和支链淀粉。支链淀粉的合成需要淀粉合成酶、分支酶和脱支酶的共同作用,而直链淀粉的合成则是在颗粒结合型淀粉合成酶的作用下进行的。颗粒结合型淀粉合成酶基因的突变造成玉米种子的腊质(糯性)表型。与支链淀粉合成的分子机制的研究相比,目前对玉米种子中直链淀粉合成的分子机制了解相对较少。以野生型黄早4玉米自交系和突变体糯玉米为实验材料,研究了种子不同发育时期直链淀粉的积累规律。通过碘染色的方法,观察了玉米种子发育过程中淀粉积累的形态变化。定量分析表明,从授粉后10d至25d,黄早4种子中直链淀粉的含量逐渐增加,同时颗粒结合型淀粉合成酶(GBSS)的活性逐渐提高;而在糯玉米中,直链淀粉和GBSS活性均未检测到。进而,通过RT-PCR方法,从黄早4种子中分离出编码GBSSI的cDNA片段。在授粉后10d至25d的玉米胚乳中均可检测到GBSSI的表达,而在胚中直到授粉后25d才检测到该基因表达的微弱信号。在糯玉米种子中没有检测到该基因的表达。研究结果表明,在玉米种子发育过程中,GBSSI基因的表达通过控制GBSS的合成,最终控制直链淀粉的合成。研究工作为理解玉米种子中直链淀粉合成的分子机制提供了重要信息。
Starch, which includes amylose and amylopectin, is the most important component in maize （Zea mays L.） seeds. The accumulation of amylose in maize seeds was examined in this study. The percentage of amylose content gradually increased in seeds from day 10 to day 25 after pollination, which is consistent with the changes of GBSS activity. The transcripts of GBSSI were detected in both the endosperm and embryo of wild-type maize. However, its transcripts, GBSS activity, and amylose were not detected in either the endosperm or embryo of waxy maize. These results indicate that the accumulation of amylose is controlled by GBSSI expression in the seeds of maize.
基金
This work was supported by the Major State Basic Research Pre-program (No. 2004CCA06900).
