Genome sequence and analysis of the tuber crop potato

Potato (Solanum tuberosum L.) is the world's most important non-grain food crop and is central to global food security. It is clonally propagated, highly heterozygous, autotetraploid, and suffers acute inbreeding depression. Here we use a homozygous doubled-monoploid potato clone to sequence and assemble 86% of the 844-megabase genome. We predict 39,031 protein-coding genes and present evidence for at least two genome duplication events indicative of a palaeopolyploid origin. As the first genome sequence of an asterid, the potato genome reveals 2,642 genes specific to this large angiosperm clade. We also sequenced a heterozygous diploid clone and show that gene presence/absence variants and other potentially deleterious mutations occur frequently and are a likely cause of inbreeding depression. Gene family expansion, tissue-specific expression and recruitment of genes to new pathways contributed to the evolution of tuber development. The potato genome sequence provides a platform for genetic improvement of this vital crop.     

Genome size variation of rhizobia

Summary Slow-growing species ofRhizobium have a genome size almost double that of the fast-growing species. This provides additional support in favor of their being placed in separate genera.     

Spontaneous robertsonian fusion leading to karyotype variation in the house mouse — First report from Asia

Summary The occurrence of spontaneous Robertsonian fusion leading to 2n=39 chromosomes (NF=40) in the house mouse (Mus musculus domesticus) has been reported for the first time from Asia. 3 phenotypically normal female mice collected from 2 distantly located populations of India (Tripura and Calcutta) show centric fusion in somatic chromosomes between pairs 2 and 16, and 8 and 14 respectively. C-banding analysis revealed that the (sub) metacentric has been originated by fusion between the broken/eroded centromeres of 2 telocentric chromosomes.     

The GTPase-activating protein Rap1GAP uses a catalytic asparagine

Rap1 is a Ras-like guanine-nucleotide-binding protein (GNBP) that is involved in a variety of signal-transduction processes. It regulates integrin-mediated cell adhesion and might activate extracellular signal-regulated kinase. Like other Ras-like GNBPs, Rap1 is regulated by guanine-nucleotide-exchange factors (GEFs) and GTPase-activating proteins (GAPs). These GAPs increase the slow intrinsic GTPase reaction of Ras-like GNBPs by many orders of magnitude and allow tight regulation of signalling. The activation mechanism involves stabilization of the catalytic glutamine of the GNBP and, in most cases, the insertion of a catalytic arginine of GAP into the active site. Rap1 is a close homologue of Ras but does not possess the catalytic glutamine essential for GTP hydrolysis in all other Ras-like and Galpha proteins. Furthermore, RapGAPs are not related to other GAPs and apparently do not use a catalytic arginine residue. Here we present the crystal structure of the catalytic domain of the Rap1-specific Rap1GAP at 2.9 A. By mutational analysis, fluorescence titration and stopped-flow kinetic assay, we demonstrate that Rap1GAP provides a catalytic asparagine to stimulate GTP hydrolysis. Implications for the disease tuberous sclerosis are discussed.     

HIV-specific cytotoxic T lymphocytes in seropositive individuals

Virus-specific cytotoxic T lymphocytes (CTL) which kill virus-infected cells are thought to be a major host defence against viral infections. Here we report the existence of human immunodeficiency virus (HIV)-specific CTL in persons infected with this virus, the aetiological agent of AIDS (acquired immunodeficiency syndrome). Recombinant HIV-vaccinia viruses were used to express HIV antigens in B-cell lines established from subjects seropositive for HIV and seronegative controls. Circulating lymphocytes capable of killing HIV env-expressing autologous B cells were detected in eight of eight seropositive subjects; in addition, at least three seropositive subjects demonstrated gag-specific cytotoxic responses. No HIV-specific cytotoxicity was observed in seronegative subjects. Selective inhibition of the env-specific cytotoxicity by a CD3-specific monoclonal antibody indicates that the effectors are T cells. This demonstration of a cytotoxic T-cell immune response to HIV in infected individuals should prove useful in investigating the immunopathogenesis of HIV infection further and in evaluating AIDS vaccine strategies.     

Effect of 3 polyphenolic compounds against ear-rot of corn incited byFusarium moniliforme Sheld

Summary Anti-F. moniliforme activity of 3 non-toxic polyphenolic compounds, viz. mangiferin, 1,3,6,7-tetrahydroxyxanthone, and 2,2,4-trihydroxybenzophenone, was evaluated. The mycotoxin-producing fungus incited ear-rot in sweet corn in fields and during storage. The test compounds provided different degrees of protection to sweet corn from the ingress of the fungus. Additionally, noteworthy postinfectional curative action was observed in the case of the trihydroxybenzophenone.Part 9 in the series Toxic substances produced byFusarium. For part 8 see S. Ghosal, K. Biswas and B.K. Chattopadhyay, Phytochemistry17, 689 (1978).     

Toxic substances produced byFusarium VI. Anti-F. oxysporum f. sp.carthami effect of 2,2′,4-trihydroxybenzophenone

Summary Anti-Fusarium oxysporum f. sp.carthami activity of 2,2,4-tri-hydroxybenzophenone was evaluated. Pretreatment with the benzophenone offered complete protection to safflower seeds and seedlings, and recovery of the latter from the fungal infection.     

Somatic chromosomes of Indian burrowing toad,Uperodon globulosum (Gunther) (Anura; Amphibia)

Summary Somatic chromosome complements of the Indian burrowing toad,Uperodon globulosum, have been described for the first time. The 2n number is 26 (NF=52) in both the sexes. No heteromorphism in relation to sex chromosome pair has been recorded. Deviations from 2n number (2n=10–28) have been noticed in the cells of different specimens. The result has been compared withU. systoma.Acknowledgment. Sincere thanks are due to Prof. P. K. Ghosh, Hooghly Mohsin College and to Dr A. K. Roy of the same college for encouragement. Thanks are due to Mr Bipul Kumar Das for his help during collection of specimen.     

A brief survey of computerized expert systems for crop protection being used in India

In the recent years, a plethora of computerized expert systems has been developed for various sectors of agriculture in India. The availability of low-cost computers, agricultural knowledge and information technology professionals are the principal reasons for the development of so many agricultural expert systems. Among all agricultural expert systems, the expert systems for crop protection need special mention. These expert systems are meant to be used by farmers and other persons without much experience of using computers. Hence, special care must be taken while developing them. The current paper develops a taxonomy for the expert systems for crop protection and briefly discusses four such expert systems for crop protection being used in India.     

Incorporation of photolabile azido fatty acid probes inNeurospora crassa andSaccharomyces cerevisiae

Summary Photolabile azido fatty acids supported the growth of fatty acid auxotrophs, thecel mutant ofNeurospora crassa and the KD115 mutant ofSaccharomyces cerevisiae. These fatty acids were incorporated into the membrane lipids of thecel and KD115 mutants, but were not used by the wild type strain.This work was presented at the 26th International Congress of Pure and Applied Chemistry, Session 1, Tokyo, September 4–10, 1977, abstracts p. 241.Support was provided by the Govt. of India to B.C. and by NCERT, New Delhi India to D.N.C.To whom requests for reprints should be sent.