Cloning and analysis of a cDNA encoding acetohydroxy acid isomeroreductase from G2 pea

Regulation of amino acid metabolic enzymes and transporters in plants

Amino acids play several critical roles in plants, from providing the building blocks of proteins to being essential metabolites interacting with many branches of metabolism. They are also important molecules that shuttle organic nitrogen through the plant. Because of this central role in nitrogen metabolism, amino acid biosynthesis, degradation, and transport are tightly regulated to meet demand in response to nitrogen and carbon availability. While much is known about the feedback regulation of the branched biosynthesis pathways by the amino acids themselves, the regulation mechanisms at the transcriptional, post-transcriptional, and protein levels remain to be identified. This review focuses mainly on the current state of our understanding of the regulation of the enzymes and transporters at the transcript level. Current results describing the effect of transcription factors and protein modifications lead to a fragmental picture that hints at multiple, complex levels of regulation that control and coordinate transport and enzyme activities. It also appears that amino acid metabolism, amino acid transport, and stress signal integration can influence each other in a so-far unpredictable fashion.

Identification of differentially expressed genes in dormant (banjhi) bud of tea (Camellia sinensis (L.) O. Kuntze) using subtractive hybridization approach

Growth regulation associated with dormancy is an essential element in plant's life cycle that leads to changes in expression of large number of genes. Forward and reverse suppression subtractive hybridization (SSH) libraries were developed to identify and characterize the genes associated with bud (banjhi) dormancy in tea (Camellia sinensis (L.) O. Kuntze). Efficiency of subtraction was confirmed by comparing the abundance of β-actin gene. A total of 17 and 45 unique sequences were obtained from forward and reverse SSH library respectively. Many of the differentially regulated genes have unknown (41.1% and 26.7%) or hypothetical functions (11.7% and 2.2%) in forward and reverse SSH library respectively, while others have a role in cell growth and metabolism. Further, semi-quantitative RT-PCR was carried out for selected genes to validate the quality of ESTs from SSH library. Gene Ontology analysis identified a greater association of these ESTs in cellular metabolic pathways and their relevance to bud dormancy. Based on the EST data, the putative role of identified genes from tea is discussed in relation to dormancy, which includes various metabolic and signalling pathways. We demonstrated that SSH is an efficient tool for enriching up- and down-regulated genes related to bud dormancy in tea. This study represents an attempt to investigate banjhi dormancy in tea under field conditions, and the findings indicate that there is a potential to develop new approaches to modulate dormancy in this species.