In vitro biochemical evaluation of cadmium tolerance mechanism in callus and seedlings of Brassica juncea.

In vitro grown callus and seedlings of Brassica juncea were treated with equimolar concentrations of cadmium and compared for their respective tolerance to cadmium. Calli cultures were grown on Murashige and Skoog medium supplemented with alpha 6-benzyl aminopurine (200 microg (-1), naphthalene acetic acid 200 microg L(-1)) and 2,4-dichloro-phenoxy acetic acid (65 microg L(-1)) while the seedlings grown on Hoagland's nutrient solution have been carried out. Cellular homeostasis and detoxification to cadmium in B. juncea were studied by analyzing the growth in terms of fresh weight and dry weight, lipid peroxidation, proline accumulation, and antioxidative enzymes (superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT)). At 200 microM cadmium, callus and seedlings showed 73.61% and 74.76% reduction in tolerance, respectively. A significant increase in malondialdehyde (MDA) content was found in both calli and seedlings; however, the amount of MDA content was more in seedlings. Proline content increased on lower concentration of cadmium (up to 50 microM), and it further decreased (up to 200 microM). But the accumulation of proline was higher in callus cultures. The overall activity of antioxidative enzymes (SOD, CAT, and APX) was found to be higher in callus in comparison to seedlings of B. juncea. Callus and seedlings showed a significant (P

Fine tuning of auxin signaling by miRNAs.

microRNAs (miRNAs) constitute a major class of endogenous non-coding regulatory small RNAs. They are present in a variety of organisms from algae to plants and play an important role in gene regulation. The miRNAs are involved in various biological processes, including differentiation, organ development, phase change, signaling, disease resistance and response to environmental stresses. This review provides a general background on the discovery, history, biogenesis and function of miRNAs. However, the focus is on the role for miRNA in controlling auxin signaling to regulate plant growth and development.