Transformation of sweet potato and expression of the transferred genes

为探索获得甘薯转基因植株的有效途径，采用农杆菌介导的愈伤组织和叶片转化再生方法进行了研究。选用6个甘薯品种和1个野生二倍体甘薯品种，以及1个瘤胃杆菌EHA101菌株。该菌株具有GUS表达载体，其中含有卡那霉素耐药基因（npt-II）和潮霉素耐药基因（hpt）。切除茎尖、叶柄和茎，与瘤胃分枝杆菌共育20分钟。将它们转移到含有抗生素的愈伤组织诱导培养基中。1个月或2个月后，诱导表达GUS基因的愈伤组织，但这些愈伤组织没有再生植株。在接下来的实验中，用2,4- d从茎尖诱导出胚性愈伤组织。该愈伤组织的植株再生频率高。将愈伤组织与结核菌共孵育3 d，获得耐药愈伤组织，部分愈伤组织形成不定胚。然而，未观察到不定胚的植株再生。以宝石和台头10号两个红薯品种为材料，建立了不诱导愈伤组织的叶片再生体系。再生植株可以直接从含有NAA的叶片中获得，也可以将由叶片形成的不定根转移到不含激素的培养基中获得。与结核菌共培养5天后，转化后的根在含抗生素的培养基上再生。然而，这些根的生长在1 ~ 2 cm长时就停止了，这些根没有再生植株。为了获得转基因甘薯植株，还需要进一步研究如何提高转化细胞和组织的再生频率。

To develop an efficient method in obtaining transgenic plants of sweet potato, Agrobacterium-mediated transformation and regeneration from calli and leaf disks were carried out. Six sweet potato cultivars and a wild diploid species (I.leucantha), and an A.tumefaciens strain, EHA101 were used. This bacterial strain has a GUS expression vector which contains a kanamycin resistant (npt-II) and a hygromycin resistant (hpt) genes.Shoot apexes, petioles and stems were excised and coincubated with A.tumefaciens for 20 min. They were transferred to a callus induction medium containing antibiotics. After one or two months, transformed calli expressig a GUS gene were induced, but no plantlet was regenerated from these calli. In the following experiment, an embryogenic callus was induced from a shoot apex with 2,4-D. A high frequency of plant regeneration was observed from this callus. By three days coincubation of the calli with A.tumefaciens, antibiotic resistant calli were obtained and adventitious embryos were formed in some of the calli. However, no plant regeneration was observed from the adventitious embryos.Plant regeneration system without callus induction was newly developed with leaf disks in two sweet potato cultivars, Jewel and Tainou No.10. Regenerated plants were obtained directly from leaf disks with NAA or obtained by transferring adventitious roots formed from leaf disks onto the medium without hormones. After a coculture with A.tumefaciens for 5 days, transformed roots were regenerated on the medium with antibiotics. However, the growth of these roots stopped in 1 to 2 cm long and no plant was regenerated from these roots.Further research is needed on the improvement of regeneration frequency from transformed cells and tissues to obtain transgenic plants of sweet potato.