Disruption of pollen tube homogalacturonan synthesis relieves pollen tube penetration defects in the Arabidopsis O-FUCOSYLTRANSFERASE1 mutant.

During angiosperm sexual reproduction, pollen tubes must penetrate through multiple cell types in the pistil to mediate successful fertilization. Although this process is highly choreographed and requires complex chemical and mechanical signaling to guide the pollen tube to its destination, aspects of our understanding of pollen tube penetration through the pistil are incomplete. Our previous work demonstrated that disruption of the Arabidopsis thaliana O-FUCOSYLTRANSFERASE1 (OFT1) gene resulted in decreased pollen tube penetration through the stigma-style interface. Here, we demonstrate that second site mutations of Arabidopsis GALACTURONOSYLTRANSFERASE 14 (GAUT14) effectively suppress the phenotype of oft1 mutants, partially restoring silique length, seed set, pollen transmission, and pollen tube penetration deficiencies in navigating the female reproductive tract. These results suggest that disruption of pectic homogalacturonan (HG) synthesis can alleviate the penetrative defects associated with the oft1 mutant and may implicate pectic HG deposition in the process of pollen tube penetration through the stigma-style interface in Arabidopsis. These results also support a model in which OFT1 function directly or indirectly modifies structural features associated with the cell wall, with the loss of oft1 leading to an imbalance in the wall composition that can be compensated for by a reduction in pectic HG deposition.

Analysis of Posttranslational Modifications in Arabidopsis Proteins and Metabolic Pathways Using the FAT-PTM Database.

Posttranslational modifications (PTMs) are critical regulators of protein behavior, and over 200 different types of PTMs have been identified. Recent developments in mass spectrometry technology and sample enrichment approaches have led to a massive expansion in the number of identified PTM types and sites within eukaryotic proteins. As these types of data become increasingly available, it is important to develop additional analysis tools and data repositories to investigate PTM cross talk and larger networks of PTMs. Recently, we developed the Functional Analysis Tools for Post-translational Modifications (FAT-PTM) database, which supports data from publicly available proteomic analyses encompassing eight different types of PTMs and over 49,000 PTM sites. In this chapter, we describe the utility of FAT-PTM for analysis of posttranslationally modified proteins in three different contexts. First, a simple protein search tool is available that allows users to investigate proteins in the Arabidopsis proteome to identify types of PTMs that are associated with the query protein as well as quantitative phosphorylation site changes associated with ten different experimental conditions. Second, FAT-PTM contains a metabolic pathway analysis tool to investigate PTMs in the broader context of over 600 different metabolic pathways compiled from the Plant Metabolic Network. Finally, FAT-PTM contains a comodification tool that can be used to identify groups of proteins that are subject to two or more user-defined PTMs. Overall, FAT-PTM provides a user-friendly platform to visualize posttranslationally modified proteins at the individual, metabolic pathway, and PTM cross-talk levels.