Applications of Molecular Biology and Genomics to Genetic Enhancement of Crop Tolerance to Abiotic Stress : a Discussion Document

The discussions on abiotic stress genomics were initiated at TAC 80 in March 2000 at ICARDA, Aleppo, Syria. Under the agenda item Trends in Science: Implications for CGIAR, TAC discussed the opportunities offered by the new sciences in improving the relevance, quality and impact of research in the CGIAR. In the area of biological sciences, TAC considered that the advances in molecular biology had important long-term implications for CGIAR’s work on genetic enhancement and how that work could be organized in the future. This paper contains three reports: 1. The report by Mike Gale dated August 2002 where he states that it is an appropriate time to tackle abiotic stress head-on, given the motivation already in place, the experience of the ARIs in technology and model systems, the knowledge among the NARS plant breeders on stressed agricultural environments, and the CGIAR Centres’ comparative advantage over mandate crops along with their links to the developing world as well as to industry.2. The report entitled "Status of Breeding for Telerance of Abiotic Stresses and Prospects for Use of Molecular Techniques" by John Bennett dated March 2001. He states that the CGIAR Centers have a comparative advantage in many aspects of abiotic stress research because of their germplasm collections, their new capacity for genetic and molecular dissection of complex traits, and their ability to conduct multidisciplinary plant improvement programs in target environments. The combined resources of the CGIAR for this work are immense but are underutilized. Investment by the CGIAR in the new tools for gene discovery will produce breakthroughs in our understanding of abiotic stress tolerance that will benefit all the mandated crops.3. The report by Hirofumi Uchimiya dated September 2001 entitled "Genetic Engineering for Abiotic Stress Tolerance in Plants"

Evolutionally conserved plant homologue of the Bax Inhibitor-1 (BI-1) gene capable of suppressing Bax-induced cell death in yeast11Accession numbers: OsBI-1, AB025926; AtBI-1, AB025927 for DDBJ/EMBL/GenBank.

AbstractThe plant homologue of Bax Inhibitor-1, a gene described to suppress the cell death induced by Bax gene expression in yeast, was isolated from Oryza sativa L. (rice) and Arabidopsis. The amino acid sequence of the predicted protein was well conserved in both animal and plant (45% in amino acids) and contained six or seven membrane-spanning segments. Northern blot analysis showed that OsBI-1 transcripts were present in all tissues examined. The OsBI-1 cDNA suppressed cell death induced by mammalian Bax in yeast, suggesting functional conservation of this BI-1 homologue in the plant kingdom

Phosphorylation of the C2 subunit of the proteasome in rice (Oryza sativa L.)

AbstractProteasomes function mainly in the ATP-dependent degradation of proteins that have been conjugated with ubiquitin. To demonstrate the phosphorylation of proteasomes in plants, we conducted an enzymatic dephosphorylation experiment with a crude extract of rice cultured cells. The results indicated that the C2 subunit of the 20S proteasome is phosphorylated in vivo in cultured cells. An in-gel kinase assay and analysis of phosphoamino acids revealed that the C2 subunit is phosphorylated by a 40-kDa serine/threonine protein kinase, the activity of which is inhibited by heparin, a specific inhibitor of casein kinase II. The catalytic subunit of casein kinase II from Arabidopsis was also able to phosphorylate the C2 subunit. These results suggest that the C2 subunit in rice is probably phosphorylated by casein kinase II. Our demonstration of the phosphorylation of proteasomes in plants suggests that phosphorylation might be involved in the general regulation of the functions of proteasomes.© 1997 Federation of European Biochemical Societies

Polypeptide composition of fraction I protein as an aid in the study of plant evolution : (chloroplast DNA, age of genera and species, origin of genomes, composition of proteins as affected by amphiploidy)

Fraction 1 protein (F-1-P), found in all green plants, consists of eight large subunits (LS) coded by chloroplast DNA and eight small subunits (SS) coded by nuclear DNA. By electrofocusing in 8M urea many different species of F-1-P from all parts of the Plant Kingdom, the LS is invariably found to resolve into three polypeptides of different isoelectric points and the SS into from one to four polypeptides. During evolution of new plant species by amphiploidy the composition of the LS is always determined by the maternal parent, but both parents make equal contributions to the composition of the SS. In the case of N. tomentosiformis (n=12; 1SS) [male sign] x N. sylvestris (n=12; 1SS) [female sign] [rightwards arrow] N. tabacum (n=24; 2SS) [male sign] x N. glutinosa (n=12; 2SS) [female sign] [rightwards arrow] N. digluta (n=36; 4SS) a F-1-P evolved containing 4SS polypeptides. None of these arose by point mutation during speciation, although the SS of F-1-P of N, digluta could have eight differences in amino acid sequence compared to N. sylvestris or N. tomentosiformis, the differences being the consequence of amphiploidy. Using this example, together with F-1-P composition in parasexual hybrids, it is hypothesized that the genetic information for more than one SS polypeptide is non-allelic and most likely located on heterologous chromosomes. The study of F-1-P in 62 species of Nicotiana provides a model system whereby the LS is an indicator of the evolutionary age of one genus relative to another and the SS an indicator of the age of one species relative to another. The SS can also serve to designate a new species of plant, while the LS has been used to trace the origin of genomes in amphiploids.HIROFUMI UCHIMIYA, KEVIN CHEN AND S. G. WILDMAN, Department of Biology Molecular Biology Institute, University of California, Los Angeles, California

Progress in Plant Protoplast Technology : Isolation, Culture and Genetic Manipulation

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