Cold resistance in plants: A mystery unresolved

Herbaceous temperate plants are capable of developing freezing tolerance when they are exposed to low nonfreezing temperatures. Acquired freezing tolerance involves extensive reprogramming of gene expression and metabolism. Recent full-genome transcript profiling studies, in combination with mutational and transgenic plant analyses, have provided a snapshot of the complex transcriptional network that operates under cold stress. The changes in expression of hundreds of genes in response to cold temperatures are followed by increases in the levels of hundreds of metabolites, some of which are known to have protective effects against the damaging effects of cold stress. Genetic analysis has revealed important roles for cellular metabolic signals, and for RNA splicing, export and secondary structure unwinding, in regulating cold-responsive gene expression and chilling and freezing tolerance. These results along with many of the others summarized here further our understanding of the basic mechanisms that plants have evolved to survive freezing temperatures. In addition, the findings have potential practical applications, as freezing temperatures are a major factor limiting the geographical locations suitable for growing crop and horticultural plants and periodically account for significant losses in plant productivity. Although, great progress has been made in the field but lacunae still remain since it appears that the cold resistance is more complex than perceived and involves more than one pathway

Functional cloning and predictive structural modeling of a novel esterase from Bacillus subtilis strain, RRL 1789.

We have recently reported the purification and characterization of a novel esterase from the Bacillus subtilis strain. In the present study we report the genomic DNA cloning and predictive structural modeling of this novel esterase. Tributyrin- and Rhodamine B-based functional screen of a Bacillus subtilis genomic library led to the identification of a potential lipolytic gene. DNA sequence analysis of the cloned gene showed that it encodes a protein of 489 amino acid residues. Sequence homology search and multiple sequence alignment showed that the protein was highly homologous to known esterases. Secondary structure-driven multiple sequence alignment with the homologous esterase of known three-dimensional structures was performed and a 3D structure model of this enzyme was constructed. Based on the topological organization of the secondary structures, this protein belongs to the alpha/beta hydrolase superfamily. Moreover, the presence of serine in the context of amino acid sequence G/A-X-S-X-G (with X an arbitrary amino acid residue) in the protein indicates that it belong to the class of serine hydrolases of this superfamily