ABSTRACT
Plants have a variety of regulatory mechanisms to perceive, transduce, and respond to biotic and abiotic stress. One such mechanism is the calcium-sensing CBL-CIPK system responsible for the sensing of specific stressors, such as drought or pathogens. CBLs perceive and bind Calcium (Ca2+) in response to stress and then interact with CIPKs to form an activated complex. This leads to the phosphorylation of downstream targets, including transporters and ion channels, and modulates transcription factor levels and the consequent levels of stress-associated genes. This review describes the mechanisms underlying the response of the CBL-CIPK pathway to biotic and abiotic stresses, including regulating ion transport channels, coordinating plant hormone signal transduction, and pathways related to ROS signaling. Investigation of the function of the CBL-CIPK pathway is important for understanding plant stress tolerance and provides a promising avenue for molecular breeding.
Subject(s)
Plant Proteins , Signal Transduction , Stress, Physiological , Stress, Physiological/genetics , Plant Proteins/genetics , Plant Proteins/metabolism , Gene Expression Regulation, Plant , Plants/genetics , Plants/metabolism , Calcium-Binding Proteins/genetics , Calcium-Binding Proteins/metabolism , Calcium/metabolism , Plant Growth Regulators/metabolism , Reactive Oxygen Species/metabolismABSTRACT
The alpha-amino group of Lys-1 and the epsilon-amino groups of Lys-41 and Lys-7 were labeled with pyridoxal 5'-phosphate (PLP) separately. The effects of GdnHCl on the activities and the fluorescence properties of the derivatives were compared. Both the fluorescence intensity and anisotropy of the probe introduced at the active site Lys-41 decreased obviously during denaturation by low concentrations of GdnHCl indicating conformational change of the active site is a parallel event to the inactivation of the enzyme. Time-correlated fluorescence lifetime measurements revealed the existence of two conformational states of PLP-modified RNase A and a shift of the conformation in favor of the slow-decay component with increasing GdnHCl concentration. The decrease in activity of RNase A at low concentrations of GdnHCl is therefore due to partial unfolding of the molecule, particularly at the active site. The experimental results of this work support the suggestion that the conformation at the active site is more easily perturbed and hence more flexible than the molecule as a whole.
