Comprehensive Proteomic Profiling of the Brassica carinata and Triticale Mature Stigma and Pollen

Abstract

Plant sexual reproduction commences with the interaction of the mature stigma (the receptive portion of the female reproductive organ) and the mature pollen (the male gametophyte). Proteins present at their mature developmental stages are therefore likely to reflect their upcoming reproductive roles. In this study, gel-free shotgun proteomics was used to investigate the proteomes of the mature stigma and pollen grain in two species that are highly related to Canada's most important crops. We identified 7703 and 5608 Brassica carinata stigma and pollen proteins, and 11533 and 2977 triticale stigma and pollen proteins, respectively. These represent the largest Brassicaceae and Triticeae pollen and stigma proteome datasets to date. In addition, this is the first comparative analysis of developing stigmas, and it was performed using isobaric tag for relative and absolute quantification (iTRAQ). There were 251 B. carinata proteins found to be differentially abundant during stigma maturation with 154 proteins that had increased abundance, while 97 decreased in abundance. For triticale, 647 differentially abundant stigma proteins were identified with 305 and 342 proteins increasing and decreasing in abundance respectively. Chapter 1 General IntroductionFlowering plants, formally classified as Magnoliophyta, but informally known as angiosperms, are the largest division within the plant kingdom. Angiosperms are divided into two main classifications; Monocots and Dicots. One of the main differences between the two is their floral structure. Flowers are important for sexual reproduction as they contain the reproductive organs of the plant (Mauseth, 1998). Many monocots and dicots are monoclinous, containing both the female (pistil) and male (stamen) reproductive organs in the same flower (Vines, 1894). Reproduction begins when pollen, released from the stamen, interacts with the stigma of the pistil, and therefore, uncovering molecular factors involved in pollen-stigma interactions is paramount to the understanding of plant reproduction. Since proteins are the mediators of physiological function within an organism, uncovering the proteome (the entire protein complement of a cell, tissue or organism) of the mature stigma and mature pollen grain, as well as the proteins that change in abundance as the stigma matures, should contribute to unraveling the molecular processes involved in pollen-stigma interactions.In this study, gel-free proteomics was used in order to elucidate key proteins underlying molecular mechanisms regulating pollen and stigma interactions in the monocot triticale and dicot Brassica carinata. As representatives of Canada's most cultivated crops, acquiring a greater understanding of the molecular processes involved in their reproduction will aid in the development of innovative approaches to managing crop reproduction.