GENE ACTION DURING REDIFFERENTIATION AND EMBRYOGENlC DEVELOPMENT IN CROPS CELLS CULTURED, IN VITRO

利用水稻、稗草、胡萝卜和马铃薯的离体培养体系，积累了有关再分化和胚性愈伤组织培养的知识。利用RT-PCR差异显示技术，观察了水稻、胡萝卜体细胞胚胎发生和稗草休眠芽形成过程中特异基因激活的生理过程。阿坝对水稻和胡萝卜胚性愈伤组织的诱导以及稗草休眠芽的诱导都有重要作用。在阿坝诱导过程中，Peroxiredoxin（Per 1）、DHa 18和VP 1基因在培养细胞中表达，在长期培养的水稻愈伤组织和稗草休眠组织中，Per 1、DHa 18和VP 1基因的表达受阿坝诱导，但在小植株再生或萌发后消失。而转录本在完整的成熟种胚中存在，在种子萌发时消失。在培养基中添加阿坝可在一定程度上维持胚性愈伤组织的培养。真核翻译起始因子5A（Eukaryotic translation initiation factor 5A，eIF-5A）是启动真核细胞蛋白质生物合成所必需的因子之一。对植物eIF-5A知之甚少。我们已经分离了编码SteIF-5A的cDNA。从马铃薯中克隆了5个差异表达的cDNA，主要分布在块茎和果实的发育过程中。这表明植物体内的抗氧化系统在代谢活跃的细胞中表达最高，植物体内具有一系列的抗氧化系统，以保护细胞免受活性氧和自由基的破坏。过氧化物酶是一种酶促抗氧化剂，其功能与作物细胞再分化过程中的非生物胁迫最为相关。

By using in vitro system of rice, bentgrass, carrot and potato, the accumulation of knowledge in redifferentiation and embryogenic callus cultures has been commenced. The physiological process of specifical gene activation was observed by the RT-PCR differential displays for somatic embryogenesis of rice, carrot and for dormant bud formation of bentgrass cultures. The role of ABA was found to be important for the induction of embryogenic callus formation in rice and carrot, and of dormant bud formation in bentgrass. On this line of research, the gene expression of peroxiredoxin (Per1) , dehydrin (DH-a18) and viviparous1 (VP1) occurred in cultured cells during the induction of ABA regime.The mRNAs of Per1, DHa18 and VP1 were induced by ABA in the long-term cultured callus of rice and dormant tissue of bentgrass cultures but disappeared after plentlet regeneration, or sprouting. While the transcripts existed in intact mature seed embryoes and disappeared when the seeds were germinating. Sustaining of the embryogenic callus cultures could be some extent achieved by the addition of ABA in medium. This hormone could be responsible for regenerating somatic embryoes and for normal embryogeny in rice plants.Eukaryotic translation initiation factor 5A(eIF-5A) is one of factors necessary for the initiation of eukaryotic cellular protein biosynthesis. Little is known in plant eIF-5A. We have isolated a cDNA encoding SteIF-5A. Five cDNA were cloned from potato showing differential expression, mainly developing tuber and fruit. This suggests that the expression is the highest in metabolic active cell.To protect cellular integrity against damage caused by reactive oxygen and free radicals, plants possess an array of antioxidant systems. Peroxiredoxins are one of enzymatic antioxidants, the functions of which are the most resposible for abiotic stresses upon redifferentiation of crop cells.