Progress in Tissue Culture and Genetic Transformation of Oil Palm: An Overview.

Oil palm (Elaeis guineensis, Jacq.) is a prominent vegetable-oil-yielding crop. Cultivating high-yielding oil palm with improved traits is a pre-requisite to meet the increasing demands of palm oil consumption. However, tissue culture and biotechnological approaches can resolve these concerns. Over the past three decades, significant research has been carried out to develop tissue culture and genetic transformation protocols for oil palm. Somatic embryogenesis is an efficient platform for the micropropagation of oil palm on a large scale. In addition, various genetic transformation techniques, including microprojectile bombardment, Agrobacterium tumefaciens mediated, Polyethylene glycol mediated mediated, and DNA microinjection, have been developed by optimizing various parameters for the efficient genetic transformation of oil palm. This review mainly emphasizes the methods established for in vitro propagation and genetic transformation of oil palm. Finally, we propose the application of the genome editing tool CRISPR/Cas9 to improve the various traits in this oil yielding crop.

Recovery of Oil Palm (Elaeis guineensis Jacq.) Somatic Embryos Cryostored For 20 Years.

　　BACKGROUND: A cryopreservation protocol has been established for oil palm somatic embryos (SEs), the efficiency of which must be evaluated, both in terms of regeneration and of long-term storage capacity, before its large-scale routine use. OBJECTIVE: To test the survival and recovery of 29 clones of oil palm somatic embryos cryostored for 20 years. MATERIALS AND METHODS: Clumps of SEs were pregrown for 7 days on medium containing 0.75 M sucrose, dehydrated in air-tight containers containing silica gel to moisture contents between 19-35% fresh weight, and then immersed directly in liquid nitrogen and stored in cryotanks for 20 years. RESULTS: Survival of SEs cryopreserved and rewarmed immediately displayed an average value of 19.1% for the 29 clones tested while survival of SEs rewarmed after 20 years of cryostorage was significantly higher, with an average of 33.2% for the 28 surviving clones. Out of these 28 surviving clones, three were lost due to contamination or regrowth decline, six produced only shoots and the rest proliferated. CONCLUSION: It is possible to cryostore oil palm SEs for extended periods and to regenerate proliferating cultures and plantlets from the cryopreserved material. The cryopreservation protocol established can thus be efficiently used to store oil palm germplasm and to manage large-scale production in industrial laboratories.

Hypoglycemic effect of an extract from date seeds on diabetic rats.

OBJECTIVE: To investigate the efficacy of an aqueous extract from date seeds on diabetic rats. METHODS: The study was performed in the Department of Anatomy, College of Medicine, King Saud University, Riyadh, Kingdom of Saudi Arabia between November 2008 and December 2009. Eighty adult albino rats were divided into 4 groups. Group 1 was used as healthy control. Group 2 was given daily ingestions of 10 ml of the date seed extract. Animals of groups 3 and 4 were made diabetic by injection of streptozotocin. Diabetic rats of group 3 received daily subcutaneous injections of 3 IU/day of insulin for 8 weeks while group 4 received ingestions of 10 ml of extract in addition to insulin. Fasting blood glucose levels were measured once weekly. Glycosylated hemoglobin (HbA1c) was also estimated. RESULTS: There is a significant change in the mean blood glucose levels between group 3 and group 4 from week 2. The mean blood glucose levels of group 4, every 2 consecutive weeks, showed a significant decrease until week 6. The HbA1c was significantly lower in group 4 compared to group 3. CONCLUSION: The hypoglycemic effect of date seed extract combined with insulin, decreases the blood glucose level significantly toward normal when compared to the effect of insulin administered as a single drug for treatment of diabetes.

Isolation and characterization of differentially expressed transcripts from the suspension cells of oil palm (Elaeis guineensis Jacq.) in response to different concentration of auxins.

Oil palm suspension cultures were initiated by transferring the gel-like friable embryogenic tissue onto liquid medium supplemented with auxins. In this study, transcripts that were differentially expressed in oil palm suspension cells cultured at different auxin concentrations were examined using suppression subtractive hybridization. Total RNA was first isolated from oil palm suspension cells proliferated in liquid medium with different hormone concentrations for 6 months. Four different hormone combinations: T1 (0.1 mg/l 2,4-D and 1.0 mg/l NAA), T2 (0.4 mg/l 2,4-D and 1.0 mg/l NAA), T3 (1.0 mg/l NAA), and T4 (0.4 mg/l 2,4-D) were used for the treatments. The first and second subtractions were performed using samples T1 and T2 in forward and reverse order. The other two subtractions were forward and reverse subtractions of T3 and T4, respectively. Reverse northern analyses showed that 14.13% of these clones were preferentially expressed in T1, 13.70% in T2, 14.75% in T3, and 15.70% in T4. Among the 294 cDNA clones that were sequenced, 61 contigs (assembled from 165 sequences) and 129 singletons were obtained. Among the 61 contigs, 10 contigs consist of sequences from treatment T1, 8 contigs were from treatment T2, 10 contigs were contains sequences of treatment T3 and 13 contigs contains sequences of treatment T4. Northern analyses of five transcripts that were shown to be differentially expressed in the oil palm suspension cells by reverse northern analysis revealed that transcripts 16A1 (a putative lignostilbene-alpha,beta-dioxygenase, EgLSD) and 16H12 (a putative ethylene responsive 6, EgER6) were differentially expressed in oil palm suspension cells treated with different levels of auxin.

Biolistic mediated production of transgenic oil palm.

Physical and biological parameters affecting DNA delivery into oil palm embryogenic calli using the biolistic device are optimized. Five different promoters are also evaluated to identify the most suitable promoter for use in oil palm transformation. Finally, the effectiveness of kanamycin, geneticin (G418), neomycin, hygromycin, and herbicide Basta as selection agents to inhibit growth of oil palm embryogenic calli is evaluated. Combination of optimized parameters, best promoter and selection agent is later used to transform oil palm embryogenic calli for producing transgenic oil palm plants. Bombarded embryogenic calli are exposed to 50 mg/l of Basta after 3 weeks. Basta-resistant embryogenic calli started to emerge five to six months in medium containing Basta. The Basta-resistant embryogenic calli are proliferated until they reach a specific size, and the Basta-resistant calli are later individually isolated and regenerated to produce complete plantlets. The complete regenerated plantlets are evaluated for the presence of transgenes by PCR, Southern and thin layer chromatography analyses.

Immature embryo: a useful tool for oil palm (Elaeis guineensis Jacq. ) genetic transformation studies

Oil palm (Elaeis guineensis Jacq.) is the highest yielding oil-bearing crop. However, being a perennial crop, genetic improvement of oil palm is extremely slow. Indeed, compared to other annual oil crops such as soybean and rapeseed, genetic manipulations remained less important. Therefore, to remain competitive, oil palm growers and breeders need new and novel approaches. In this report, the potential of immature embryos (IE) as a useful tool for oil palm genetic transformation studies was evaluated. It was evident that IEs were amenable to both direct and Agrobacterium-mediated gene transfer. Due to the abundant supply of IE, optimization of biolistic and Agrobacterium-mediated gene transfer into IEs were easily carried out. Transient transformation frequencies were comparable to other plant systems reported, with as high as 97.4 percent recorded for biolistic and 64.4 percent for Agrobacterium-mediated gene transfer. Like most moncots, oil palm tissues were less sensitive to kanamycin, geneticin and chloramphenicol. Instead, both hygromycin and phosphinotrycin were toxic 20 mg/l, making both suitable candidates for selecting putative transformants. IEs were also more responsive to in vitro manipulations as compared to other explants such as leaf and root tissues. Rapid in vitro response to callusing and embryogenesis or rapid and highly efficient direct germination resulted in a shorter culture period. This would minimize the production of abnormal clonal palms, which has been associated to chromosomal aberration due to prolonged time in culture. In addition, IEs also allows rapid and direct introduction of elite genes into breeding programs and in biclonal seed production.