Whole-Organ analysis of calcium behaviour in the developing pistil of olive (<it>Olea europaea </it>L.) as a tool for the determination of key events in sexual plant reproduction

• Main Authors: Zienkiewicz Krzysztof, Rejón Juan D, Suárez Cynthia, Castro Antonio J, de Dios Alché Juan, Rodríguez García María
• Format: Article
• Language: English
• Published: BMC 2011-11-01
• Series: BMC Plant Biology
• Online Access: http://www.biomedcentral.com/1471-2229/11/150

<p>Abstract</p> <p>Background</p> <p>The pistil is a place where multiple interactions between cells of different types, origin, and function occur. Ca²⁺is one of the key signal molecules in plants and animals. Despite the numerous studies on Ca²⁺signalling during pollen-pistil interactions, which constitute one of the main topics of plant physiology, studies on Ca²⁺dynamics in the pistil during flower formation are scarce. The purpose of this study was to analyze the contents and <it>in situ </it>localization of Ca²⁺at the whole-organ level in the pistil of olive during the whole course of flower development.</p> <p>Results</p> <p>The obtained results showed significant changes in Ca²⁺levels and distribution during olive pistil development. In the flower buds, the lowest levels of detectable Ca²⁺were observed. As flower development proceeded, the Ca²⁺amount in the pistil successively increased and reached the highest levels just after anther dehiscence. When the anthers and petals fell down a dramatic but not complete drop in calcium contents occurred in all pistil parts. <it>In situ </it>Ca²⁺localization showed a gradual accumulation on the stigma, and further expansion toward the style and the ovary after anther dehiscence. At the post-anthesis phase, the Ca²⁺signal on the stigmatic surface decreased, but in the ovary a specific accumulation of calcium was observed only in one of the four ovules. Ultrastructural localization confirmed the presence of Ca²⁺in the intracellular matrix and in the exudate secreted by stigmatic papillae.</p> <p>Conclusions</p> <p>This is the first report to analyze calcium in the olive pistil during its development. According to our results <it>in situ </it>calcium localization by Fluo-3 AM injection is an effective tool to follow the pistil maturity degree and the spatial organization of calcium-dependent events of sexual reproduction occurring in developing pistil of angiosperms. The progressive increase of the Ca²⁺pool during olive pistil development shown by us reflects the degree of pistil maturity. Ca²⁺distribution at flower anthesis reflects the spatio-functional relationship of calcium with pollen-stigma interaction, progamic phase, fertilization and stigma senescence.</p>