烟草原胚中赤霉素GA_7与GA_4分布的免疫电镜观察

DISTRIBUTION OF GIBBERELLINS A7 AND A4 IN TOBACCO PROEMBRYOS USING IMMUNOELECTRON MICROSCOPY

烟草原胚中赤霉素ＧＡ７与ＧＡ４分布的免疫电镜观察陈以峰１梁世平１杨弘远２郑志富２周燮１（武汉大学生命科学学院植物生殖生物学研究室武汉４３００７２）２（南京农业大学农学系南京２１００９５）关键词原胚，赤霉素，免疫电镜定位，烟草ＤＩＳＴＲＩＢＵＴＩＯＮＯ...

The ovules of Nicotiana tabacum var. macrophylla 8 days after pollination were fixed successively with 2% EDC (1ethyl3(3dimethylaminopropyl) carbodiimide) and a mixture solution of paraformaldehyde and glutaraldehyde, then slightly postfixed in 0.5% osmium solution. Ultrathin sections of 6, 9 or 12 celled proembryos embedded in Epon 812 resin were stained in an antiGA MAb and sheep antimouse IgGcolloidal gold (10 nm). This MAb specifically recognizes methyl esters of GA7 and GA4.Therefore, it could be used as a probe to localize GA7 and GA4 in cells after EDC fixation. The 12celled proembryo is composed of a 9celled embryo and a 3celled suspensor. Wide distribution of GA7 and GA4 was observed in all proembryo cells and most or ganelles at subcellular level, including walls, plasmodesmata, plasma membrane, cytoplasmic matrix, mitochondria, plastids, vacuoles, endoplasmic reticulum and nuclei. Clusters of gold granules were found in nuclear envelope, nucleomatrix, nucleolus, chromosome, cytoplamic matrix. In a region composed of cytoplasmic matrix, a vacuole and a mitochondrium, such concentrated gold granules were particularly obviously observed. There appeared a gradient distribution of GA7 and GA4 from embryo cells decreasingly to suspensor cells. GA7 and GA4 could be translocated via intercellular walls, plasmodesmata and vesicles between embryo and suspensor. The authors suspect the direction of GA translocation in proembryo may be from suspensor to embryo. To author's knowledge, this is the first report to indicate subcellular and gradient distributions of bioactive gibberellins in plant proembryos. 