小麦体细胞胚发生中DNA、RNA和蛋白质的合成动态

CHANGES IN THE SYNTHESIS OF DNA,RNA AND PROTEIN DURING SOMATIC EMBRYOGENESIS IN WHEAT(Tritocum aestivum L.)

用普通小麦的幼胚在Ｎ６Ｂ５ＭＳⅠ培养基上诱导出胚性和非胚性愈伤组织，将这两种愈伤组织分别转至Ｎ６Ｂ５ＭＳⅡ培养基后，胚性愈伤组织形成许多体细胞胚，非胚性愈伤组织形成不定苗。胚性愈伤组织转入Ｎ６Ｂ５ＭＳⅡ培养基后，第２～４ｄ形成胚性细胞，二细胞、四细胞原胚，８ｄ后，则以多细胞原胚为主，１２～２４ｄ后，可见球形胚和梨形胚，２６ｄ后则多为成熟胚。利用放射性同位素液体闪烁计数技术结合核酸、蛋白质合成抑制剂，研究了以小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）幼胚为外植体诱导产生体细胞胚的发生、发育过程中ＤＮＡ、ＲＮＡ和蛋白质的合成动态。发现ＲＮＡ、蛋白质的合成分别在胚性愈伤组织培养后的第４和第８ｄ就达到高峰，ＤＮＡ的合成也明显增加，但变化平缓。而非胚性愈伤组织中的核酸和蛋白质的合成速率远远低于胚性愈伤组织。加入抑制剂后，不仅抑制了核酸、蛋白质的合成，同时也抑制了胚性愈伤组织的生长和体细胞胚的发生、发育，加入时间越早，抑制效应越明显。可见，ＤＮＡ、ＲＮＡ和蛋白质是体细胞胚发生、发育的分子基础。

Embryogenic and non embryogenic callus formed from immature embryo of wheat( Triticum aestivum L.)in N 6B 5MS medium Ⅰ supplemented with 2,4 D 2mg/L,KT 0 5 mg/L, LH 300mg/L, sucrose 3% were sub cultured and transferred respectively to N 6B 5MS medium Ⅱ(2,4 D was decreased to 0 5mg/L and 4mol/L proline was added).Somatic embryos obtained from embryogenic callus,and plantlet formed from non embryogenic callus through organogenesis respectively. By incorporation of 3H thymidine, 3H uridine and 3H leucine into DNA,RNA and protein respectively,the rate of synthesis of DNA,RNA and protein during somatic embryogenesis were measured.A large amount of RNA and protein synthesized during the early somatic embryogenesis.The activities of RNA and protein synthesis reached the peak on the 4th and the 8th day respectively,then decreased a little,but kept a high level.The synthesis of DNA increased apparently during the early stage.No apparent change occurred when the embryogenic cell masses formed.The synthesis rate of RNA and protein in non embryogenic callus were much less than that in embryogenic callus. Actinomycin and cycloheximide inhibited not only the synthesis of nucleic acid and protein,but also the growth of embryogenic callus and somatic embryogenesis.The earlier the inhibitors were added,the greater the influnence was caused.The results indicate that the active expression of corresponding genes of wheat is the molecular base of somatic embryogenesis.