2(5) 2009 September issue 
September 2009 issue
Southern Cross Publisher©2009

RSS Feed
Current status of research on o-acetylserine (thiol) lyase and ß-cyanoalanine synthase, two enzymes of plant cysteine biosynthesis- a review

Annabelle U. Novero


The production of cysteine is the first major significant event in the plant sulfate assimilation process. Cysteine is a precursor of many important biological molecules. Two of the enzymes involved in cysteine biosynthesis are ß-cyanoalanine synthase (CAS) and o-acetylserine (thiol) lyase, members of the Beta-subsituted alanine synthase (Bsas) gene family. There were about forty Bsas genes cloned and characterized from a wide range of plant families in a span of about two decades. Some information on the molecular and biochemical characteristics, as well as subcellular localization of the Bsas genes were recorded.  Several reports concurred that the Bsas genes are regulated by external factors such as sulfur and nitrogen availability. More research work toward the elucidation of as many cysteine biosynthesis genes as possible is needed because the biochemical functions of majority of such genes deposited in the databases have not yet been proven. The results will have direct applications in sulfur-related genetic engineering of plants such as breeding for higher protein content.

Keywords: sulfate assimilation; cysteine synthase; gene expression

Pages 181-189 Full Text PDF 
Effect of FeSO4 and pH on shoot regeneration from the cotyledonary explants of Tossa Jute

Huda, K.M.K., Bhuiyan, M.S.R., Zeba, N., Banu S.A., Mahmud, F. and Khatun A.


Contamination free healthy seedling is required for plant regeneration. In order to achieve this, seeds of tossa jute were germinated on both agar supported hormone free MS medium and cotton supported hormone free liquid MS medium in vitro. Percentage of seeds germinated on cotton supported medium was found to be much higher (97.6%) than seeds germinated on agar (45.8%) supported medium. Seedlings grown on cotton supported medium were healthier than the seedling grown on agar supported medium.  To optimize the FeSO4 concentration and pH level for in vitro shoot regeneration from the cotyledon explants of tossa jute (var. O-9897 and O-72), the explants were inoculated onto MS medium (0.5 mg/l IAA and 3.0 mg/l BAP) which was maintained with different concentrations of FeSO4 (0, 28, 56, 84 and 112 mg/l) and a wide range of pH levels (4.0 to 7.5). The highest rate of shoot regeneration was achieved in a shoot-regenerating medium with 56 mg/l FeSO4 and a pH of 5.5. Shoot multiplication and growth rate were significantly affected by different concentrations of FeSO4. Shoots were not formed in a FeSO4 free medium. Percentage shoot regeneration and number of shoots produced per explant were significantly affected by the pH but both variety respond well in pH 5.5. When the pH was adjusted below or above 5.5, the growth rate of the shoot significantly decreased.

C. olitorius; cotton-supported MS medium; genotype; micropropagation; multiplication; morphogenesis

Pages 190-196 Full Text PDF
Plant growth, metabolism and adaptation in relation to stress conditions. XXIV. Salinity-biofertility interactive effects on proline, glycine and various antioxidants in Lactuca sativa

M. E. Younis, M. N. A. Hasaneen, and S. M. N. Tourky


Proline and glycine contents in lettuce plants appeared to show additional significant increments, in response to treatment with phosphorein biofertilizer, above those increments maintained in response to salinization. Administration of nitrobein biofertilizer to the NaCl media led to significant increases in proline and glycine contents above the water control levels, but the amino acid content of NaCl-treated plants appeared consistently higher than that content in NaCl + nitrobein-treated plants. Supplemental addition of phosphorein to the salinized culture media induced significant increases in the contents of antioxidant compounds, throughout the experimental period. As compared with the saline control values, total ascorbate (ASA + DASA) and total glutathione (GSSG + GSH) contents were found either to decrease (with 4 & 6 mmhos NaCl) or to increase (with 8 & 10 mmhos NaCl) significantly in response to addition of nitrobein to the saline culture media. The activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APO) and glutathione reductase (GR) in the salinized lettuce plants fortified with the recommended dose of phosphorein or nitrobein were, in general, significantly up-regulated above the salinized control levels; the magnitude of up-regulation being dependent on the concentration of NaCl, the stage of growth and on the enzyme under investigation. With lettuce plants, the present results are discussed in relation to applicability of two biofertilizers to sodic salty soils in Egypt.            

Pages 197-205 Full Text PDF
Identification of a short putative 5' regulatory sequence from transgenic hairy root of tomato-regulating specific expression pattern

Chan Kok Fei, Ismanizan Ismail, Siti Izera Ismail, Dinesh Natorajan and  Zamri Zainal


The Solanum lycopersicum cultivar MT1 was transformed by the A4 strain of Agrobacterium rhizogenes harboring the promoter trapping binary vector pPRF120. Transformed hairy root lines generated from the transformation were verified for stable expression of the inserted gus (ß-glucuronidase) transgene in the genomic DNA. The 68i line was found to be stably transformed by pPRF120 via PCR analysis. This positive line was used for further study to detect promoter sequences that control expression of the integrated T-DNA, which contains a promoterless gus reporter gene. By using a ‘DNA walking’ approach, a single unknown flanking sequence was successfully amplified by two rounds of adaptor ligation PCR (AL-PCR). The AL-PCR patterns obtained were specific and reproducible for a given genomic library. AL-PCR products from the genomic libraries digested with either DraI (clone 1B) or HpaI (clone 5B) contain ~350 bp and ~1400 bp of upstream region respectively. The alignment of the sequences from clones 1B and 5B showed a very high percentage of similarity (97%). Resulting BLASTn analysis of the 5B clone indicated that 183 bp was 97% similar to chromosome 11 of Solanum lycopersicum, whereas 1105 bp was 97% similar to integrated Ri plasmid agropine of A. rhizogenes strain A4 for complete TL-DNA. The bioinformatics-based characterization of the short 256 bp putative novel promoter region directly upstream of T-DNA insertion via PlantCARE revealed the presence of several motifs for plant transcription factors such as circadian, TGA-element and motifs involved in light responsive control including CATT, ATCT, Sp1 and G-box.

Keywords: Agrobacterium rhizogenes; cis-acting elements; insertional mutagenesis; Solanum lycopersicum; promoter trapping; T-DNA tagging

Pages 206-213 Full Text PDF
Genetic diversity and assessment of drought tolerant sorghum landraces based on
morph-physiological traits at different growth stages

Muhammad Amjad Ali, Shahid Niaz, Amjad Abbas, Waseem Sabir and Khawar Jabran


Root morphology and leaf water relations are important morph-physiological traits for screening various crop plants under water stress. In this study these morph-physiological traits were measured to sort out drought tolerant local landraces (LLRs) of sorghum. The results revealed that the landrace FJSS-1 performed the best for most of the characters followed by FJSS-11 and FJSS-17 which also performed well for various traits contributing towards water stress tolerance at seedling and post-flowering stages. The landrace, FJSS-10 revealed the contrasting parents showing drought susceptibility. Cluster analysis clearly divided the LLRs in two groups out of which Cluster I displayed more scope for selection against water stress. Dry root weight exhibited the highest genotypic coefficient of variation among seedling traits while excise leaf weight loss among the flag leaf related characters. Considerable degree of variation among the LLRs for most of the traits proposed these genotypes as significant source for the selection of water stress tolerance. In the same way, higher amount of heritability and genetic advance for the most of the morph-physiological parameters advocated that elevated amount of genetic gain for these parameters might be possible followed by hybridization. Our results suggest that these morpho-physiological traits could be efficiently used as selection criteria for drought tolerance in sorghum at different growth stages.

Key words:
Morph-physiological traits, drought tolerance, seedling, flag leaf, sorghum landraces

Pages 214-227 Full Text PDF