Dynamics of protein expression during pollen germination in canola (Brassica napus)

Abstract

The proteome of mature (MP) and in vitro germinating pollen (GP) of canola (Brassica napus) were analyzed using the DIGE technology with the objective of identifying proteins and their function in pollen germination. Of the 2,238 protein spots detected in gel images, 344 were differentially expressed in MP and GP samples of which 165 were subjected to MALDI-TOF/TOF and 130 were successfully identified using the NCBInr and Brassica EST databases. The major proteins up-regulated in GP, relative to MP, have roles in carbohydrate metabolism, protein metabolism, and cell wall remodeling. Others with roles in cytoskeleton dynamics, nucleotide and amino acid metabolism, signal transduction, and stress response also showed higher expression in GP. Proteins concerned with transcriptional regulation and ion transport were similar in MP and GP, and some catalases and LEA proteins were down-regulated in GP. A number of proteins including, oleosin, cruciferin, and enolase, were released into the pollen germination medium indicating their potential role in pollen-stigma interaction. Glycosylated proteins were also identified in MP and GP, but their protein profiles were not different. This study has documented the dynamics of protein expression during pollen germination and early tube growth in B. napus and provides insights into the fundamental mechanisms involved in these processes, and in cell growth, cell-cell communication, and cell signaling.

Pollen vacuoles and their significance

“…Several vacuolar ion channels, such as H ? -ATPase or calcium channels, appear to be expressed at all stages of pollen development (Jakobsen et al 2005;Peiter et al 2005;Bock et al 2006) and during germination and pollen tube growth (Pertl et al 2009;Sheoran et al 2009). Strompen et al (2005) found that vacuolar H ?…”

How to shape a cylinder: pollen tube as a model system for the generation of complex cellular geometry

“…Local activation of enzymes affecting cell wall chemistry is likely to be involved in the process. The expression of expansins and such enzymes as xyloglucan endotransglycosylase/hydrolase, polygalacturonases, pectate lyases and pectin esterases in hydrating or germinating pollen (Holmes-Davis et al 2005;Noir et al 2005;Pina et al 2005;Dai et al 2007;Russell et al 2008;Sheoran et al 2009) suggests possible involvement of these proteins in cell wall softening, but the exact timing and subcellular location of these protein activities in relation to pollen germination are poorly understood. There is also the question of whether these proteins are targeted to the pollen grain's own cell wall or to the apoplast of the stigmatic and transmitting tissues, with the aim of dissolving mechanical obstacles.…”

Cytological and Proteomic Analyses of Osmunda cinnamomea Germinating Spores Reveal Characteristics of Fern Spore Germination and Rhizoid Tip Growth*

“…However, the fern spore germination happens in the medium, therefore, it is somewhat more complex and affected by various environmental factors, such as light, gravity, calcium, phytohormone, and temperature (6). The protein functional skew in fern spores and pollen grains revealed from this study and recent proteomics studies on germinating pollen from kiwifruit (Actinidia deliciosa) (71,72), Nicotiana tabacum (73), rice (Oryza sativa) (26), Brassica napus (74), Pinus strobus (75), Picea meyeri (76,77), Picea wilsonii (78) and Arabidopsis (79,80) presented new evidence for the differentiation of fern spores and spermatophyte pollen (Fig. 10).…”

“…No photosynthetic proteins were found in pollen. This highlights that the remodeling of pollen tube cell wall, the loosening and hydrolyzing stigma surface cell and transmitting track of pistil, The data of germinating pollen were summarized and reclassified based on pollen proteomic studies on Oryza sativa (26), Actinidia deliciosa (71,72), Nicotiana tabacum (73), Brassica napus (74), Pinus strobus (75), Picea meyeri (76,77), Picea wilsonii (78), and Arabidopsis thaliana (79,80). The y axis represents the reclassified functional categories, and the x axis shows the percentage of identified proteins.…”