Abstract
The tapetum is a single layer of secretory cells which encloses the anther locule and sustains pollen development and maturation. Upon apoptosis, the remnants of the tapetal cells, consisting mostly of lipids and proteins, fill the pits of the sculpted exine to form the bulk of the pollen coat. This extracellular matrix forms an impermeable barrier that protects the male gametophyte from water loss and UV light. It also aids pollen adhesion and hydration and retains small signaling compounds involved in pollen–stigma communication. In this study, we have updated the list of the pollen coat’s protein components and also discussed their functions in the context of sexual reproduction
Highlights
Sexual reproduction is essential for the propagation of higher plants
The olive pollen coat proteome consisted of at least 16 pollen coat protein (PCP) with molecular weights ranging from 10 to 75 kDa, while up to 31 different pollen released proteins (PRPs) were observed in the 8–100 kDa range after analysis of the culture medium (Figure 2)
Pollen coat proteins are essential for pollen adhesion and hydration, pollen–stigma recognition and communication, pollen germination and stigma invasion
Summary
Sexual reproduction is essential for the propagation of higher plants. From an agronomical point of view, this is a key process as fertilization ensures seed and fruit formation in fruit crop species. “tryphine” [4], is an extracellular matrix derived from the anther tapetum It is deposited on the outermost surface of the pollen grain following tapetal cell breakdown, filling the spaces and cavities of the highly sculpted exine (Figure 1a). The pollen coat contains aa number number of of proteins, proteins, most most of of which which are are synthesized in the tapetum layer. Glucanase, cysteine protease xylanase enzymes stored vesicles, vacuoles and thethe cytosol, surface in vesicles, vacuoles and cytosol,respectively, respectively,and andeventually eventuallydeposited depositedon on the the pollen pollen surface following tapetal apoptosis [17] Some of these proteins undergo further proteolytic processing in following tapetal apoptosis [17]. Pollen coat lipids and proteins contribute to pollen adhesion and play a key role in pollen rehydration on dry-type stigmatic surfaces [19,20]. We provide a comprehensive and updated list of pollen coat proteins and discuss their putative biological functions in plant reproduction
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