Dissecting Arabidopsis thaliana DICER function in small RNA processing, gene silencing and DNA methylation patterning.

Small RNAs have several important biological functions. MicroRNAs (miRNAs) and trans-acting small interfering RNAs (tasiRNAs) regulate mRNA stability and translation, and siRNAs cause post-transcriptional gene silencing of transposons, viruses and transgenes and are important in both the establishment and maintenance of cytosine DNA methylation. Here, we study the role of the four Arabidopsis thaliana DICER-LIKE genes (DCL1-DCL4) in these processes. Sequencing of small RNAs from a dcl2 dcl3 dcl4 triple mutant showed markedly reduced tasiRNA and siRNA production and indicated that DCL1, in addition to its role as the major enzyme for processing miRNAs, has a previously unknown role in the production of small RNAs from endogenous inverted repeats. DCL2, DCL3 and DCL4 showed functional redundancy in siRNA and tasiRNA production and in the establishment and maintenance of DNA methylation. Our studies also suggest that asymmetric DNA methylation can be maintained by pathways that do not require siRNAs.

An ARGONAUTE4-containing nuclear processing center colocalized with Cajal bodies in Arabidopsis thaliana.

ARGONAUTE4 (AGO4) and RNA polymerase IV (Pol IV) are required for DNA methylation guided by 24 nucleotide small interfering RNAs (siRNAs) in Arabidopsis thaliana. Here we show that AGO4 localizes to nucleolus-associated bodies along with the Pol IV subunit NRPD1b; the small nuclear RNA (snRNA) binding protein SmD3; and two markers of Cajal bodies, trimethylguanosine-capped snRNAs and the U2 snRNA binding protein U2B''. AGO4 interacts with the C-terminal domain of NRPD1b, and AGO4 protein stability depends on upstream factors that synthesize siRNAs. AGO4 is also found, along with the DNA methyltransferase DRM2, throughout the nucleus at presumed DNA methylation target sites. Cajal bodies are conserved sites for the maturation of ribonucleoprotein complexes. Our results suggest a function for Cajal bodies as a center for the assembly of an AGO4/NRPD1b/siRNA complex, facilitating its function in RNA-directed gene silencing at target loci.

FY is an RNA 3' end-processing factor that interacts with FCA to control the Arabidopsis floral transition

The nuclear RNA binding protein, FCA, promotes Arabidopsis reproductive development. FCA contains a WW protein interaction domain that is essential for FCA function. We have identified FY as a protein partner for this domain. FY belongs to a highly conserved group of eukaryotic proteins represented in Saccharomyces cerevisiae by the RNA 3' end-processing factor, Pfs2p. FY regulates RNA 3' end processing in Arabidopsis as evidenced through its role in FCA regulation. FCA expression is autoregulated through the use of different polyadenylation sites within the FCA pre-mRNA, and the FCA/FY interaction is required for efficient selection of the promoter-proximal polyadenylation site. The FCA/FY interaction is also required for the downregulation of the floral repressor FLC. We propose that FCA controls 3' end formation of specific transcripts and that in higher eukaryotes, proteins homologous to FY may have evolved as sites of association for regulators of RNA 3' end processing.

Red and white meat of tuna (Euthynnus affinis): their biochemical role and nutritional quality

The biochemical and nutrient compositions of red and white meat of tuna are reported. Based on the data the biochemical role and nutritional quality of red and white meat are discussed. The results show that red meat is adapted for slow and continuous activity and white meat for quick but occasional activity. In spite of comparatively low lysine content the red meat is adjudged more nutritious than white meat.

Bacteriology of spoilage of canned prawns

Spoilage characteristics of different types of bacteria isolated from bacteriologically defective cans and processing factory environs were studied by inoculating pure cultures into sterile prawn meat. The pattern of spoilage, namely, production of off odour, bulging of the cans and disintegration of meat were observed. Data on spoilage under aerobic as well as anaerobic conditions are presented. Most of the cultures produced some kind of spoilage, though differences were observed in the extent of spoilage produced by different types of bacteria. Gram positive spore formers were found to be the major spoilers and the extent of spoilage was more with mixed cultures.

Canning of squid

A simple method for canning squid (Loligo sp.) is discussed. Hot blanching the dressed meat in 7% brine containing 0.2% citric acid for 5 min, packing and subsequent filling with 2% brine containing 0.2% citric acid and processing at 1.0 kg/cm² steam for 20 mm gave an excellent canned product with good shelf-life.

Prediction of drained weight in canned prawn under commercial conditions

A general formula for the prediction of drained weight of canned prawn processed under laboratory condition has been worked out earlier (Chaudhuri et al., 1978). Attempts were made in this communication to modify the general formula to predict the drained weight under commercial conditions of processing particularly blanching, as the moisture content of meat depends on the quantum of heat received during blanching (Govindan, 1975).

Physics in fish processing technology

To design, develop and put into operation an equipment either to increase the productivity or to improve the existing technique to obtain a better quality of the product, the fishery engineer/scientist should have a comprehensive knowledge of fundamental principles involved in the process. Many a technique in fish processing technology, whether it applies to freezing, dehydration or canning, involves always a type of heat transfer, which is dependent to a certain extent on the external physical parameters like temperature. humidity, pressure, air flow etc. and also on the thermodynamic properties of fish muscle in the temperature ranges encountered. Similarly informations on other physical values like dielectric constant and dielectric loss in the design of quick trawlers and in quality assessment of frozen/iced fish, refractive index and viscosity in the measurement of the saturation and polymerisation of fish oils and shear strength in the judgement of textural qualities of cooked fish are also equally important.

A proforma for assessment of the levels of sanitation in fish processing establishments

Over the past 15 years of its development, the fish processing industry in India has shown considerable improvement in maintenance of hygiene during handling of the raw material, processing and marketing of the finished product. This is best manifested in the lowering of upper limits of bacterial loads in factory environs and in processed products (Pillai, 1971). More care and attention is given by the processors in recent years in the scientific cleaning and sanitizing of utensils and equipment, chlorination of water supplies and personnel hygiene. An example of sanitation score form is given to help scientists and technologists to evaluate the hygienic status of the processing units.

Quality tolerances for water for use in fish processing

A survey on the sources and quality of water used in prawn processing factories has revealed much non-uniformity in the chemical quality. An attempt has been made to study the effect of varying concentrations of chemical constituents in the water used for prawn freezing and its influence on the quality of the prawn after freezing and during cold storage. The results of the study are reported in this communication, together with recommendations on the quality tolerances for water used in fish processing industry.

Quality control in the Indian fish processing industry

Quality control is defined as the continuing assessment of a current operation. It is usually the responsibility of an individual or a department directly responsible to the management. In the case of fish and fishery products, quality control includes all the steps taken to protect the quality of the material since catch until it reaches the consumer.

Technological aspects of preservation and processing of edible shell fishes V. Cold storage changes in mussels (Mytilus edulis) and clams (Villortia [i.e. Villorita] sp.)

The changes in chemical, bacteriological and organoleptic qualities of mussels and clams during freezing and subsequent frozen storage have been studied in relation to the holding time in ice prior to freezing and the shelf-life of the product is determined.

Biochemical differences between the red and white meat of tuna and changes in quality during freezing and storage

The differences between the white and red (dark) meat of tuna (Katsuwonus pelamis) in chemical, physical and organoleptic aspects and the rate and pattern of spoilage during freezing and subsequent storage are discussed in this communication. In the indices studied distinct difference is seen between the white and red meat as well as in the head, middle and tail portions of the same fish. The characteristic colour of tuna meat is due to the presence of haemoglobin and myoglobin, the concentrations of which are about 5 times more in red meat than in white meat. The shelf-life of the frozen material varies with the type of the pack, that is, whole fish>chunks>fillets; the fillets being adversely affected during frozen storage.

Processing aspects of Indian mackerel: a review

Indian mackerel belongs to the family Scombridae and the genus Rastrelliger. The Indian mackerel, Rastrelliger kanagurta (Cuvier), is a pelagic shoaling fish widely distributed in the Indo Pacific region with maximum abundance in Indian coasts. Another species, R. brachysoma (Bleeker), also is reported from the Andamans in Indian waters. However, the former is the species that supports the fishery in India (Nair, 1970).

Survey on the idle capacity of fish processing (freezing) plants in India - 1. West Coast

The extent of idle capacity in fish processing (freezing) plants estimated by stratified random sampling is reported. The estimates for 1978 and 1979 for the processing plants on the west coast of India were 76.9 % and 73.2 % respectively at the rate of 250 working days per annum and two shifts per day. The percentage error of estimates worked out to 6.04 for 1978 and 6.98 for 1979. Substantial under utilization of processing plants noticed in all the states accounts mainly to the non-availability of raw material (prawn), high cost of production and shortage of power.