Apomixis: an enigma with potential applications

Apomixis has been the focus of research in plant sciences in recent years with lot of scope for crop improvement. It results in clonal progeny without fertilization, having maternal genetic constitution. The impact of introducing apomixis in crop plants could be significant mainly for its use in fixation of hybrid vigour. Because of epigenetic barriers, introgression of apomixis from a close relative to a sexual crop plant by conventional plant breeding methods could not generate expected results. Recent developments in plant molecular biology and biotechnology can help in developing potential strategies. This article summarizes various aspects of apomixis research that are being followed in India and abroad

Expression of a rice chitinase gene enhances antifungal potential in transgenic grapevine (Vitis vinifera L.)

To enhance the antifungal potential of grapevine, transgenic plants were generated by transferring rice chitinase gene under a maize-ubiquitin promoter along with its first intron into the leaf disc-induced somatic embryos via Agrobacterium mediated transformation. After co-cultivation for 2 days with recombinant Agrobacterium, somatic embryos were transferred onto WPM medium containing BAP 1.5 μM and NAA 0.1 μM supplemented with 25 mg/L hygromycin. Secondary or tertiary embryos were selected and the antibiotic resistant transgenic plantlets were analyzed. The integration and stability of the transgene were confirmed by PCR, RT-PCR, Southern blotting and by Western blot analyses. The transgenic plants exhibited higher chitinase activity than the non-transformed plants. These analyses indicated that the foreign gene was translated into the protein of expected molecular weight that showed chitinase activity. Following in vitro inoculation of powdery mildew (Uncinula necator), the transgenic plants showed delayed onset of the disease and smaller lesions. The transgenic plants were adapted to the greenhouse and did not show any phenotypic alterations.

Transcriptional Downregulation of Rice rpL32 Gene under Abiotic Stress Is Associated with Removal of Transcription Factors within the Promoter Region

Background: The regulation of ribosomal proteins in plants under stress conditions has not been well studied. Although a few reports have shown stress-specific post-transcriptional and translational mechanisms involved in downregulation of ribosomal proteins yet stress-responsive transcriptional regulation of ribosomal proteins is largely unknown in plants. Methodology/Principal Findings: In the present work, transcriptional regulation of genes encoding rice 60S ribosomal protein L32 (rpL32) in response to salt stress has been studied. Northern and RT-PCR analyses showed a significant downregulation of rpL32 transcripts under abiotic stress conditions in rice. Of the four rpL32 genes in rice genome, the gene on chromosome 8 (rpL32_8.1) showed a higher degree of stress-responsive downregulation in salt sensitive rice variety than in tolerant one and its expression reverted to its original level upon withdrawal of stress. The nuclear run-on and promoter:reporter assays revealed that the downregulation of this gene is transcriptional and originates within the promoter region. Using in vivo footprinting and electrophoretic mobility shift assay (EMSA), cis-elements in the promoter of rpL32_8.1 showing reduced binding to proteins in shoots of salt stressed rice seedlings were identified. Conclusions: The present work is one of the few reports on study of stress downregulated genes. The data revealed that rpL32 gene is transcriptionally downregulated under abiotic stress in rice and that this transcriptional downregulation i

The influence and possible recombination of genotypes on the production of microspore embryoids in anther cultures of Solanum tuberosum and dihaploid hybrids

In addition to physical and chemical factors, genotype appears to be a very important factor influencing success in anther culture. Recombination by making crosses with selected responding clones has been introduced as a possible helpful method to positively influence the success and response type via the factor genotype. From the progeny of such a cross, one genotype could be selected, producing in 30 to 40 percent of the cultured anthers, fully developed embryoids and plantlets, which are a mixture of polyploids, dihaploids and monohaploids. Further, a pleiotropic marker embryo spot visible as a nodal band in the plant stage, has been used to confirm the microsporic origin of dihaploids and polyploids and to prove their homozygous nature. This marker also shows potential use in confirming the origin of calli from individual microspores

Induction of haploidy from pollen grains in angiosperms - the current status

Since the successful induction of haploids from anthers cultured in vitro in 1964, a great deal of attention has been given to this problem by those interested in obtaining pure lines and mutants for crop improvement and biochemical genetics. In the last 16 years the anther culture technique has been refined and extended to over one hundred and fifty different species. More recently, isolated pollen culture - which is a refinement of the original anther culture technique - has also been developed. In this review we have made an effort to critically examine existing reports with the objective of analysing the effects of various factors - e.g. culture medium, the cultural conditions, and the effect of genotype and physiological state of the parent plant on pollen induction - and to speculate on the mechanism of action of different factors in order to throw some light on the process of haploid induction