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

利用水稻、弯草、胡萝卜和马铃薯的离体体系，开始了再分化和胚性愈伤组织培养方面的知识积累。利用RT-PCR技术对水稻、胡萝卜体细胞胚发生和弯草培养物的休眠芽形成进行了差异显示，观察了特定基因激活的生理过程。ABA对水稻和胡萝卜的胚性愈伤组织形成以及弯草的休眠芽形成具有重要的诱导作用。在这方面的研究中，在ABA诱导下，培养细胞中发生了过氧化物还氧蛋白（Per1）、脱氢蛋白（DH-a18）和胎生蛋白（VP1）的基因表达。ABA在长期培养的水稻愈伤组织和bentgrass休眠组织中诱导了Per1、DHa18和VP1 mrna，但在小块再生或出芽后消失。而转录本在完整的成熟种子胚胎中存在，在种子萌发过程中消失。在培养基中添加ABA可在一定程度上维持胚性愈伤组织的培养。这种激素可能与水稻体细胞胚胎的再生和正常胚胎发生有关。真核生物翻译起始因子5A（Eukaryotic translation initiation factor 5A, eIF-5A）是真核细胞蛋白生物合成起始所必需的因子之一。我们对植物的eIF-5A知之甚少。我们分离到了一个编码SteIF-5A的cDNA。从马铃薯中克隆了5个差异表达的cDNA，主要发育块茎和果实。这说明在代谢活跃细胞中表达量最高。为了保护细胞免受活性氧和自由基的损害，植物具有一系列的抗氧化系统。过氧化物还毒素是一种酶促抗氧化剂，其功能对作物细胞再分化过程中的非生物胁迫最为重要。

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.