Comparative Proteomic Analysis of Genotypic Variation in Germination and Early Seedling Growth of Chickpea under Suboptimal Soil-Water Conditions

Protein expression patterns in imbibed seeds of three cultivars of chickpea (Cicer arietinum L.) with different rates of germination under limiting water supply in soil (>10% water holding capacity) were compared. A large number of soluble proteins expressed earlier and at higher levels in cv Rupali seeds compared to two other genotypes that germinated less rapidly (KH850) or not at all (KJ850). Among the proteins identified were those with chaperone-like functions, including LEA and HSP proteins and proteins involved in metabolism of reactive oxygen species (ROS). Only NAD-malate dehydrogenase was identified as an early, differentially abundant enzyme of the TCA cycle, but in cv Rupali, expression of phospho-enol-pyruvate carboxykinase rose very rapidly to a high level, indicating that an anaplerotic C input to the TCA cycle may have been important. Proteinase inhibitors were more highly expressed in the genotype that did not germinate compared to cv Rupali. Clustering analysis of proteomic data indicated a link between groups of proteins, implying a common regulatory mechanism possibly at the transcriptional level. The chaperone-like proteins and enzymes of ROS homeostasis provide a useful starting point for molecular genetic analysis that may well identify other important genes for the early germination trait.