%0 Journal Article
%T Characterization of a caleosin expressed during olive (Olea europaea L.) pollen ontogeny
%A Krzysztof Zienkiewicz
%A Agnieszka Zienkiewicz
%A Mar¨ªa Rodr¨ªguez-Garc¨ªa
%A Antonio J Castro
%J BMC Plant Biology
%D 2011
%I BioMed Central
%R 10.1186/1471-2229-11-122
%X A 30 kDa caleosin was identified in the anther tissues by Western blot analysis. Using fluorescence and transmission electron microscopic immunolocalization methods, the protein was first localized in the tapetal cells at the free microspore stage. Caleosins were released to the anther locule and further deposited onto the sculptures of the pollen exine. As anthers developed, tapetal cells showed the presence of structures constituted by caleosin-containing lipid droplets closely packed and enclosed by ER-derived cisternae and vesicles. After tapetal cells lost their integrity, the caleosin-containing remnants of the tapetum filled the cavities of the mature pollen exine, forming the pollen coat. In developing microspores, this caleosin was initially detected on the exine sculptures. During pollen maturation, caleosin levels progressively increased in the vegetative cell, concurrently with the number of oil bodies. The olive pollen caleosin was able to bind calcium in vitro. Moreover, PEGylation experiments supported the structural conformation model suggested for caleosins from seed oil bodies.In the olive anther, a caleosin is expressed in both the tapetal and germ line cells, with its synthesis independently regulated. The pollen oil body-associated caleosin is synthesized by the vegetative cell, whereas the protein located on the pollen exine and its coating has a sporophytic origin. The biological significance of the caleosin in the reproductive process in species possessing lipid-storing pollen might depend on its subcellular emplacement. The pollen inner caleosin may be involved in OB biogenesis during pollen maturation. The protein located on the outside might rather play a function in pollen-stigma interaction during pollen hydration and germination.In Angiosperms, stamens are the floral organs where pollen development occurs. Each stamen typically consists of a stalk (i.e. the filament) and a bilobed anther with four pollen sacs or microsporangia [1]. In a
%U http://www.biomedcentral.com/1471-2229/11/122