Low Eng-Ti L, Alias Halimah, Boon Soo-Heong, Shariff Elyana M, Tan Chi-Yee A, Ooi Leslie Cl, Cheah Suan-Choo, Raha Abdul-Rahim, Wan Kiew-Lian, Singh Rajinder
Advanced Biotechnology and Breeding Centre, Biology Division, Malaysian Palm Oil Board (MPOB), 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor DE, Malaysia.
BMC Plant Biol. 2008 May 29;8:62. doi: 10.1186/1471-2229-8-62.
Oil palm (Elaeis guineensis Jacq.) is one of the most important oil bearing crops in the world. However, genetic improvement of oil palm through conventional breeding is extremely slow and costly, as the breeding cycle can take up to 10 years. This has brought about interest in vegetative propagation of oil palm. Since the introduction of oil palm tissue culture in the 1970s, clonal propagation has proven to be useful, not only in producing uniform planting materials, but also in the development of the genetic engineering programme. Despite considerable progress in improving the tissue culture techniques, the callusing and embryogenesis rates from proliferating callus cultures remain very low. Thus, understanding the gene diversity and expression profiles in oil palm tissue culture is critical in increasing the efficiency of these processes.
A total of 12 standard cDNA libraries, representing three main developmental stages in oil palm tissue culture, were generated in this study. Random sequencing of clones from these cDNA libraries generated 17,599 expressed sequence tags (ESTs). The ESTs were analysed, annotated and assembled to generate 9,584 putative unigenes distributed in 3,268 consensi and 6,316 singletons. These unigenes were assigned putative functions based on similarity and gene ontology annotations. Cluster analysis, which surveyed the relatedness of each library based on the abundance of ESTs in each consensus, revealed that lipid transfer proteins were highly expressed in embryogenic tissues. A glutathione S-transferase was found to be highly expressed in non-embryogenic callus. Further analysis of the unigenes identified 648 non-redundant simple sequence repeats and 211 putative full-length open reading frames.
This study has provided an overview of genes expressed during oil palm tissue culture. Candidate genes with expression that are modulated during tissue culture were identified. However, in order to confirm whether these genes are suitable as early markers for embryogenesis, the genes need to be tested on earlier stages of tissue culture and a wider range of genotypes. This collection of ESTs is an important resource for genetic and genome analyses of the oil palm, particularly during tissue culture development.
油棕（Elaeis guineensis Jacq.）是世界上最重要的油料作物之一。然而，通过传统育种对油棕进行遗传改良极其缓慢且成本高昂，因为育种周期可能长达10年。这引发了人们对油棕营养繁殖的兴趣。自20世纪70年代引入油棕组织培养以来，克隆繁殖已被证明是有用的，不仅可用于生产均匀的种植材料，还对基因工程计划的开展有帮助。尽管在改进组织培养技术方面取得了相当大的进展，但增殖愈伤组织培养的愈伤形成和胚胎发生率仍然很低。因此，了解油棕组织培养中的基因多样性和表达谱对于提高这些过程的效率至关重要。
本研究共构建了12个标准cDNA文库，代表油棕组织培养的三个主要发育阶段。对这些cDNA文库中的克隆进行随机测序，产生了17599个表达序列标签（EST）。对EST进行分析、注释和组装，生成了9584个推定的单基因，分布在3268个重叠群和6316个单拷贝中。这些单基因根据相似性和基因本体注释被赋予推定功能。聚类分析基于每个重叠群中EST的丰度调查了每个文库的相关性，结果显示脂质转移蛋白在胚性组织中高度表达。发现一种谷胱甘肽S-转移酶在非胚性愈伤组织中高度表达。对单基因的进一步分析鉴定出648个非冗余简单序列重复和211个推定的全长开放阅读框。
本研究概述了油棕组织培养过程中表达的基因。鉴定出了在组织培养过程中表达受到调控的候选基因。然而，为了确认这些基因是否适合作为胚胎发生的早期标记，需要在组织培养的早期阶段和更广泛的基因型上对这些基因进行测试。这个EST集合是油棕遗传和基因组分析的重要资源，特别是在组织培养发育过程中。
