ARC-Small Grain, Field Crops, Division, Private Bag X29, Bethlehem, 9700, South Africa.
ARC-Biometry, Private Bag X5013, Stellenbosch, 7599, South Africa.
Protoplasma. 2022 Mar;259(2):453-468. doi: 10.1007/s00709-021-01684-4. Epub 2021 Jun 30.
Ionizing irradiation induces positive or negative changes in plant growth (M1) depending on the amount of irradiation applied to seeds or plant parts. The effect of 50-350 Gy gamma irradiation of kernels on nucleolar activity, as an indicator of metabolic activity, in root tip cells of tetraploid wheat Triticum turgidum ssp. durum L. cv. Orania (AABB) was investigated. The number of nucleoli present in nuclei and micronuclei as well as the mitotic index in the different irradiation dosages was used as an indicator of the cells entering mitosis, the chromosomes with nucleolar organizer regions that are active as well as chromosome doubling in the event of unsuccessful mitotic division. Nucleolar activity was investigated from 17.5 to 47.5 h after the onset of imbibition to study the first mitotic division and its consequences on the cells that were in G and G phases at the time of gamma irradiation. Untreated material produced a maximum of four nucleoli formed by the nucleolar organizing regions (NORs) on chromosomes 1B and 6B. In irradiated material, additional nucleoli were noted that are due to the activation of the NORs on chromosome 1A in micronuclei. The onset of mitosis was highly significantly retarded in comparison to the control due to checkpoints in the G phase for the repairing of damaged DNA. This study is the first to report on the appearance of nucleoli in micronuclei as well as activation of NORs in the micronuclei that are inactive in the nucleus and the effect of chromosome doubling on nucleolar activity in the event of unsuccessful mitotic division.
电离辐射会根据种子或植物部分接受的辐射量，对植物生长产生正向或负向的变化（M1）。本研究以四倍体小麦（Triticum turgidum ssp. durum L. cv. Orania）根尖细胞为材料，用 50-350Gyγ射线辐照麦粒，研究麦粒核仁作为代谢活性的指示物，对根尖细胞的核仁活性的影响。用不同辐照剂量下核仁、微核中核仁的数量和有丝分裂指数作为有丝分裂细胞进入、具有活性核仁组织区的染色体以及染色体加倍的指标，用于研究未能成功进行有丝分裂的细胞。在吸水后 17.5-47.5h 进行核仁活性检测，研究第一次有丝分裂及其对有丝分裂时处于 G1 期和 G2 期的细胞的影响。未经处理的材料最多形成四个核仁，由染色体 1B 和 6B 上的核仁组织区（NOR）组成。在辐照材料中，微核中额外的核仁是由于染色体 1A 上的 NOR 被激活所致。与对照组相比，由于 G 期存在用于修复受损 DNA 的检查点，有丝分裂的开始明显延迟。本研究首次报道了微核中核仁的出现以及微核中核仁组织区的激活，这些核仁在核内是无活性的，并且在有丝分裂失败时，染色体加倍对核仁活性的影响。
