Postharvest biology and technology of sapota: a concise review

Sapota is cultivated in many countries of tropical and subtropical climate. It is delicious, nutritive, and commercially grown mainly for fresh consumption. Postharvest life of sapota is very short due to its highly perishable nature and other many reasons such as quick ripening, faster senescence, rapid loss of moisture, microbial spoilage, and fruit sensitivity to cold storage. To maintain and/or increase the shelf life of sapota, proper postharvest management is required. Unfortunately, very little work has been done so far, with limited success, leaving scarce literature published on postharvest management technologies of sapota. Different pre and postharvest treatments to reduce metabolic activity and quality loss have been suggested. Moreover, proper storage temperature and packaging may be used to increase the shelf life of fruits. This review explores the postharvest technologies adopted to enhance the shelf life of sapota during storage and distribution channel.     

Ecological developmental biology: developmental biology meets the real world

The production of phenotype is regulated by differential gene expression. However, the regulators of gene expression need not all reside within the embryo. Environmental factors, such as temperature, photoperiod, diet, population density, or the presence of predators, can produce specific phenotypes, presumably by altering gene-expression patterns. The field of ecological developmental biology seeks to look at development in the real world of predators, competitors, and changing seasons. Ecological concerns had played a major role in the formation of experimental embryology, and they are returning as the need for knowledge about the effects of environmental change on embryos and larvae becomes crucial. This essay reviews some of the areas of ecological developmental biology, concentrating on new studies of amphibia and Homo.     

Application of recombinant DNA technology to plant protection: molecular approaches to engineering virus resistance in crop plants

Developments in plant tissue culture, plant transformation and regeneration, and improvements in techniques to isolate and manipulate viral genes have led to the exploitation of the concept of cross protection: turning the virus onto itself and controlling it with its own genes. By introducing and expressing genes of viral origin in crop plants, scientists have engineered resistance to several plant viruses. Some of the approaches, used singly or in combination, include expression of viral-coat protein, untranslatable sense or antisense RNA, satellite RNA, virusspecific neutralizing antibody genes, plant viral replicase, protease or movement proteins and defective, interfering RNA. All of these approaches have resulted in manifestation of virus resistance to varying degrees in several commercially important crop plants. This review summarizes the recent advances in engineering virus resistance using the above approaches, and lists specific examples of their use in cultivated crop plants of economic importance.H.R. Pappu and C.L. Niblett are with the Plant Pathology Department, University of Florida. Gainesville, FL 32611-0680, USA; R.F. Lee is with the Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA. Florida Agricultural Experiment Station Journal Series No. R-04558.     

Environmental implications of recombinant DNA technology

Applications of recombinant DNA technology are discussed as a backdrop for evaluation of the environmental impacts of this technology. Some of applications include using traditional biological techniques for specific purposes, including nitrogen fixation, microbial pesticides, and waste treatment. In these instances the final product lies along a continuum, beginning with an organism marginally performing its function, and ending with one that is highly specialised and very efficient in what it does. One may move along this continuum toward the ‘perfect’ microorganism by using traditional methodologies of mutagenesis and selection, recombinant DNA technology, or a combination of the two.     

Historical DNA as a tool to address key questions in avian biology and evolution: A review of methods,challenges, applications,and future directions

Museum specimens play a crucial role in addressing key questions in systematics, evolution, ecology, and conservation. With the advent of high‐throughput sequencing technologies, specimens that have long been the foundation of important biological discoveries can inform new perspectives as sources of genomic data. Despite the many possibilities associated with analyzing DNA from historical specimens, several challenges persist. Using avian systems as a model, we review DNA extraction protocols, sequencing technologies, and capture methods that are helping researchers overcome some of these difficulties. We highlight empirical examples in which researchers have used these technologies to address fundamental questions related to avian conservation and evolution. Increasing accessibility to new sequencing technologies will provide researchers with tools to tap into the wealth of information contained within our valuable natural history collections.     

The developmental biology of cementum.

In conclusion, we have reviewed an extensive literature on early cementogenesis and performed a detailed morphological and molecular analysis to illustrate and verify key issues in the current debate about epithelial and mesenchymal contributions to root cementum. We have demonstrated that prior to cementogenesis, Hertwig's epithelial root sheath disintegrates and dental follicle cells penetrate the epithelial layer to invade the root surface. Our studies confirmed that HERS became disrupted or disintegrated prior to cementum deposition. We visualized how mesenchymal cells from the dental follicle penetrated the HERS bilayer and deposited initial cementum, while immediately adjacent epithelial cells were separated from the root surface by a basal lamina and did not secrete any cementum. Human specimen from the Gottlieb collection indicated that HERS was removed from the root surface prior to cementum deposition. Our in situ hybridization and immolocalization data revealed that both amelogenin mRNAs and enamel proteins were restricted to the crown enamel and were absent from the root surface and from the cervical-most ameloblasts adjacent to the root margin. On Western blots, cementum protein extracts did not cross-react with amelogenin antibodies. Our studies in conjunction with our literature review together confirmed the classical theory of cementum as a dental follicle derived connective tissue that forms subsequent to HERS disintegration.     

Telomere biology of trypanosomatids: beginning to answer some questions

Studies of telomere structure and maintenance in trypanosomatids have provided insights into the evolutionary origin and conservation of some telomeric components shared by trypanosomes and vertebrates. For example, trypanosomatid telomeres are maintained by telomerase and consist of the canonical TTAGGG repeats, which in Trypanosoma brucei can form telomeric loops (t-loops). However, the telomeric chromatin of trypanosomatids is composed of organism-specific proteins and other proteins that share little sequence similarity with their vertebrate counterparts. Because telomere maintenance mechanisms are essential for genome stability, we propose that the particular features shown by the trypanosome telomeric chromatin hold the key for the design of antiparasitic drugs.     

Molecular biology of plasminogen activators and recombinant DNA progress

Plasminogen activators are enzymes with multiple roles. They play vital parts in maintaining the functional integrity of the vascular system and they are also involved in processes of tissue reorganization. In this review, the molecular properties of these enzymes that make them ideal targets for genetic and biochemical engineering to satisfy a potential therapeutic role are described.     

Development of new thrombolytic agents using recombinant DNA technology.

The increasing incidence of thromboembolic diseases has sustained the search for new agents able to stimulate the natural fibrinolytic system. The first generation of antithrombotic agents include bacterial streptokinase and human urine urokinase. Because these molecules lack specificity for the fibrin clot, important efforts have been made to produce, using recombinant DNA technology, agents presenting higher fibrin clot selectivity such as t-PA (tissue-type plasminogen activator) and scu-PA (single chain urokinase-type plasminogen activator). In parallel, several laboratories are presently attempting to create mutants and hybrids plasminogen activators displaying improved thrombolytic properties with respect to the natural molecules. In this paper, we describe briefly the mechanisms of fibrinolysis and the role of the different natural thrombolytic agents. In addition, we review the possibilities of genetic engineering for the production of natural and novel plasminogen activators.     

Gyrodactylid developmental biology: historical review, current status and future trends

In the viviparous gyrodactylids, embryos develop one inside another within the parental uterus, a phenomenon with major implications for the biology of this species-rich group. Development occurs via two routes: first-born daughters develop at the centre of an embryo cluster in utero, whereas all other daughters develop from oocytes. The resulting offspring are, however, morphologically indistinguishable. We review here the history of gyrodactylid embryology in the context of current knowledge and, present additional cytogenetic and ultrastructural observations of embryonic development. These progenetic parasites are highly modified for viviparity; oocyte maturation and sperm storage occur in a single chamber, the Egg Cell Forming Region, and a mature oocyte passes into the uterus after the birth of the preceding, fully developed offspring. The uterus has a syncytial lining derived from anterior and posterior cap cells. These cells are the first to differentiate in the female reproductive system and may be involved in controlling development. Embryos receive nutrients via the uterus rather than from vitelline cells. Traditionally, development of the first-born daughter has been considered a form of polyembryony, although paedogenesis has also been suggested. In contrast to previous studies, we could not trace lineage of the first-born daughter to a single quiescent macromere. However, only mitotic divisions have been conclusively observed in the intraembryonic generation, indicating an asexual origin. All other daughters are formed from meiotically derived oocytes by sexual reproduction or automictic parthenogenesis. The latter may involve pre-meiotic doubling of chromosomes, but the precise mechanism and the relative proportion of sexual and parthenogenetic offspring are unknown. Exceptionally, cleavage in Gyrodactylus spp. occurs by duets rather than quartets (a pattern previously only recorded in acoels) and is characterised by extensive cell rearrangements. Blastomeres may be connected by fine cytoplasmic processes or completely disassociated and are readily redistributed by the muscular actions of the parental uterus. This process resembles 'Blastomeren-Anarchie' of rhabdocoels but without the structural support of vitelline cells. It prevents generation of early cell fate maps and indicates regulative, rather than mosaic, development. Structures such as the gut and excretory system differentiate late, and are highlighted, together with the attachment apparatus, as examples of post-embryonic differentiation. Molecular and cellular techniques are now essential to further elucidate mechanisms of gyrodactylid reproduction, which will in turn contribute to current debates with animal embryology.     

Beyond Arabidopsis. Translational biology meets evolutionary developmental biology

Developmental processes shape plant morphologies, which constitute important adaptive traits selected for during evolution. Identifying the genes that act in developmental pathways and determining how they are modified during evolution is the focus of the field of evolutionary developmental biology, or evo-devo. Knowledge of genetic pathways in the plant model Arabidopsis serves as the starting point for investigating how the toolkit of developmental pathways has been used and reused to form different plant body plans. One productive approach is to identify genes in other species that are orthologous to genes known to control developmental pathways in Arabidopsis and then determine what changes have occurred in the protein coding sequence or in the gene's expression to produce an altered morphology. A second approach relies on natural variation among wild populations or crop plants. Natural variation can be exploited to identify quantitative trait loci that underlie important developmental traits and, thus, define those genes that are responsible for adaptive changes. The possibility of applying comparative genomics approaches to Arabidopsis and related species promises profound new insights into the interplay of evolution and development.