Genetic and environmental factors contribute to variation in cell wall composition in mature desi chickpea (Cicer arietinum L.) cotyledons.

Chickpea (Cicer arietinum L.) is an important nutritionally rich legume crop that is consumed worldwide. Prior to cooking, desi chickpea seeds are most often dehulled and cleaved to release the split cotyledons, referred to as dhal. Compositional variation between desi genotypes has a significant impact on nutritional quality and downstream processing, and this has been investigated mainly in terms of starch and protein content. Studies in pulses such as bean and lupin have also implicated cell wall polysaccharides in cooking time variation, but the underlying relationship between desi chickpea cotyledon composition and cooking performance remains unclear. Here, we utilized a variety of chemical and immunohistological assays to examine details of polysaccharide composition, structure, abundance, and location within the desi chickpea cotyledon. Pectic polysaccharides were the most abundant cell wall components, and differences in monosaccharide and glycosidic linkage content suggest both environmental and genetic factors contribute to cotyledon composition. Genotype-specific differences were identified in arabinan structure, pectin methylesterification, and calcium-mediated pectin dimerization. These differences were replicated in distinct field sites and suggest a potentially important role for cell wall polysaccharides and their underlying regulatory machinery in the control of cooking time in chickpea.

Mass Spectrometry Imaging of Metabolites in Barley Grain Tissues.

Higher plants are composed of a multitude of tissues with particular functions, reflected by distinct profiles of transcripts, proteins, and metabolites. Although the rapid development of "omics" technologies has advanced plant science tremendously within recent years, analysis is frequently performed on whole organ or whole plant extracts, causing the loss of spatial information. Mass spectrometry-based imaging (MSI) approaches have become a powerful tool to decipher spatially resolved molecular information. Matrix-assisted laser desorption/ionization (MALDI) is the most widespread ionization method utilized for MSI and has recently been applied to plant science. A range of different plant organs and tissues has been successfully analyzed by MSI, and patterns of various classes of metabolites from primary and secondary metabolism have been obtained. This protocol describes a method for analysis of spatial metabolite distributions in cryosections of developing barley grains. Detailed procedures for sample preparation, mass spectrometry measurement, and data analysis are provided. © 2016 by John Wiley & Sons, Inc.