We are grateful to the Director, Directorate of Weed Science Research (ICAR), Jabalpur, MP, India, for providing the research facilities to complete the PG dissertation work of S.S. “
“Microorganisms are responsible for the decomposition of plant litter due selleck kinase inhibitor to their enhanced enzyme capabilities. Among extracellular enzymes, those involved in lignin decomposition are especially relevant in leaf degradation. However, the knowledge of the bacterial contribution to the decomposition of phenol-derived compounds in submerged leaf litter is

limited. We have used the large unit of the multicomponent bacterial phenol hydroxylase (LmpH) as a genetic proxy to describe changes in the phenol-degrading bacterial community during the decomposition of Platanus acerifolia leaves in a forested stream. Significant differences were found in the phenol-degrading community when three decomposition stages, initial (day 7), midterm (day 58), and late (day 112), were compared. Estimated Shannon’s diversity values decreased significantly from 1.93 (initial) to 0.98 (late). According to the deduced amino acid sequences and

the corresponding theoretical kinetic parameters of phenol hydroxylases, the initial community showed a low degree of specialization, presumably resulting from random colonization of leaves. At the late decomposition stage, the bacterial community became more specialized, and LmpH genes similar to high-affinity phenol hydroxylases of Comamonas sp. and Burkholderia cepacia increased. The observed Sulfite dehydrogenase Metformin clinical trial changes in the bacterial community suggested an active role of bacteria during litter decomposition in aquatic environments. In forested rivers and streams, the input of leaf litter from riparian vegetation represents a fundamental organic matter source for microbial decomposers (Pascoal et al., 2003; Gulis et al., 2008). Fungi and bacteria decompose and mineralize plant material, which then enters the river food web (Hieber & Gessner, 2002). The most

important microbial enzymes for leaf litter decomposition are those that break down plant fibers, such as cellulases, hemicellulases, pectinases, and phenol oxidases (Sinsabaugh et al., 2002). During leaf litter decomposition, different enzymatic activities may arise in function of the available material in the leaf and of the biodegradability and/or recalcitrance of this material. Because lignin is one of the most recalcitrant compounds, its specific degradation might be a relevant limiting step for complete mineralization of plant material. Major enzymes involved in lignin degradation include phenol oxidases, which oxidize phenols at the expense of oxygen. Phenol oxidase activity has been related to an increase in the relative content of lignin and free phenolic compounds (Sinsabaugh, 2010; Artigas et al., 2011).

Eleven of the 55 secondary metabolite clusters were upregulated at the lower temperature, including aflatoxin biosynthesis genes, which were among the most highly upexpressed genes. On average, transcript abundance for the 30 aflatoxin biosynthesis genes was 3300 times greater at 30 °C as compared with 37 °C. The results are consistent with the

view that high temperature negatively affects selleckchem aflatoxin production by turning down transcription of the two key transcriptional regulators, aflR and aflS. Subtle changes in the expression levels of aflS to aflR appear to control transcription activation of the aflatoxin cluster. Aspergillus flavus produces aflatoxins B1 and B2 and causes aflatoxin contamination of preharvest crops such as corn, cotton, peanuts and tree nuts, and postharvest grains during storage (Bhatnagar et al., 1987; Bennett & Klich, 2003). The discovery of the first stable aflatoxin precursor, norsolorinic acid (Bennett, 1981), paved the way

for the elucidation of the aflatoxin biosynthetic pathway, including its intermediates and biosynthetic gene clusters in A. flavus, Aspergillus parasiticus, Aspergillus nidulans (sterigmatocystin as end product), Aspergillus sojae and Aspergillus oryzae (nonfunctional gene cluster) (Brown et al., 1996; Yu et al., 2004a, b). Aflatoxin biosynthesis is affected by many biotic and abiotic factors (Payne & Brown, 1998; Yu et al., 2010). The influence of temperature Aspartate on aflatoxin formation has been reported previously (Schroeder & Hein, 1968; Ogundero, 1987). The optimum Bleomycin chemical structure temperature for biosynthesis of aflatoxin and other secondary metabolites is at 30 °C; while the optimum temperature for fungal growth is at about 37 °C but it is less optimal for mycotoxin production. Sequencing of the A. flavus genome facilitated the construction of microarrays, which have been used to study transcriptional

regulation of aflatoxin biosynthesis at different temperatures (OBrian et al., 2007; Georgianna et al., 2008, 2010; Payne et al., 2008; Schmidt-Heydt et al., 2009). These studies identified a large number of genes expressed at high level under low temperature. The effect of temperature on natural antisense transcript expression was also reported (Smith et al., 2008). While microarrays are a robust tool for genome-wide gene expression analysis, they have been plagued by high background and low sensitivity problems. For regulatory genes with low level of expression, microarrays often fail to provide meaningful information about their expression levels. Thus, no published microarray experiments have provided an accurate estimate of the aflR and aflS expression levels. RNA-Seq technology has been successful for transcriptome profiling in a closely related species, A. oryzae (Wang et al., 2010).