Wheat leaf senescence and its regulatory gene network

Wheat leaf senescence is a developmental process that involves expressional changes in thousands of genes that ultimately impact grain protein content(GPC), grain yield(GY), and nitrogen use efficiency.The onset and rate of senescence are strongly influenced by plant hormones and environmental factors e.g. nitrogen availability. At maturity, decrease in nitrogen uptake could enhance N remobilization from leaves and stem to grain, eventually leading to leaf senescence. Early senescence is related to high GPC and somewhat low yield whereas late senescence is often related to high yield and somewhat low GPC. Early or late senescence is principally regulated by up and down-regulation of senescence associated genes. Integration of external and internal factors together with genotypic variation influence senescence associated genes in a developmental age dependent manner. Although regulation of genes involved in senescence has been studied in rice, Arabidopsis, maize, and currently in wheat, there are genotypespecific variations yet to explore. A major effort is needed to understand the interaction of positive and negative senescence regulators in determining the onset of senescence. In wheat, increasing attention has been paid to understand the role of positive senescence regulator, e.g. GPC-1, regulated gene network during early senescence time course. Recently, gene regulatory network involved early to late senescence time course revealed important senescence regulators. However, the known negative senescence regulator Ta NAC-S gene has not been extensively studied in wheat and little is known about its value in breeding. Existing data on senescence-related transcriptome studies and gene regulatory network could effectively be used for functional study in developing nitrogen efficient wheat varieties.

Non-escaping frost tolerant QTL linked genetic loci at reproductive stage in six wheat DH populations

Reproductive stage frost poses a major constraint for wheat production in countries such as Australia.However,little progress has been made in identifying key genes to overcome the constraint.In the present study,a severe frost event hit two large-scale field trials consisting of six doubled haploid(DH)wheat populations at reproductive stage(young microspore stage)in Western Australia,leading to the identification of 30 robust frost QTL on 17 chromosomes.The major 18 QTL with the phenotype variation over 9.5%were located on 13 chromosomes including 2 A,2 B,2 D,3 A,4 A,4 B,4 D,5 A,5 D,6 D,7 A,7 B and7 D.Most frost QTL were closely linked to the QTL of anthesis,maturity,Zadok stages as well as linked to anthesis related genes.Out of those,six QTL were repetitively detected on the homologous regions on 2 B,4 B,4 D,5 A,5 D,7 A in more than two populations.Results showed that the frost damage is associated with alleles of Vrn-A1 a,Vrn-D1 a,Rht-B1 b,Rht-D1 b,and the high copy number of Ppd-B1.However,anthesis QTL and anthesis related genes of Vrn-B1 a and Ta FT3-1 B on chromosomes 5 B and 1 B did not lead to frost damage,indicating that these early-flowering phenotype related genes are compatible with frost tolerance and thus can be utilised in breeding.Our results also indicate that wild-type alleles Rht-B1 a and Rht-D1 a can be used when breeding for frost-tolerant varieties without delaying flowering time.

Comparative Antibiotic Sensitivity Pattern of Hospital and Community Acquired <i>Staphylococcus aureus</i>Isolates of Jessore, Bangladesh

Staphylococcus aureus has emerged over the past several decades as a leading cause of hospital acquired infections, which are more commonly termed as nosocomial infections. In recent years, strains of this bacterium which are resistant against several types of antibiotics have evolved and their prevalence is becoming a potential epidemiological threat. As there are limited data available on antibiotic resistance patterns of S. aureus that are isolated from hospital, the study was undertaken. The study was conducted by collecting swab samples from the hospital environment & volunteers and then identified them by standard methods. In case of hospital isolates, highest percentage of resistance was shown against Erythromycin (88.89%) and Ampicillin (83.33%). Significant resistance was also observed in cases of Ciprofloxacin (33.33%) and Tetracycline (33.33%). Lowest percentage of resistance was shown against Streptomycin (11.11%) and Vancomycin shows only intermediate resistant pattern (11.11%). On the other hand, community isolates were 100% sensitive against four antibiotics except Ampicillin (60% resistant) and Vancomycin (20% resistant). From the result it is easily discernable that, there are significant differences in the resistance pattern among hospital environment isolates and community acquired isolates. Samples were collected from different locations of hospital surgery room e.g. floor, wall, operating bed, trolley, sitting tool, cabinet etc. As anticipated, highest number of isolates showing resistance against these antibiotics were from the tool used for sitting.