Abstract
Reactive oxygen species (ROS) are produced in the olive reproductive organs as the result of intense metabolism. ROS production and pattern of distribution depend on the developmental stage, supposedly playing a broad panel of functions, which include defense and signaling between pollen and pistil. Among ROS-producing mechanisms, plasma membrane NADPH-oxidase activity is being highlighted in plant tissues, and two enzymes of this type have been characterized in Arabidopsis thaliana pollen (RbohH and RbohJ), playing important roles in pollen physiology. Besides, pollen from different species has shown distinct ROS production mechanism and patterns of distribution. In the olive reproductive tissues, a significant production of superoxide has been described. However, the enzymes responsible for such generation are unknown. Here, we have identified an Rboh-type gene (OeRbohH), mainly expressed in olive pollen. OeRbohH possesses a high degree of identity with RbohH and RbohJ from Arabidopsis, sharing most structural features and motifs. Immunohistochemistry experiments allowed us to localize OeRbohH throughout pollen ontogeny as well as during pollen tube elongation. Furthermore, the balanced activity of tip-localized OeRbohH during pollen tube growth has been shown to be important for normal pollen physiology. This was evidenced by the fact that overexpression caused abnormal phenotypes, whereas incubation with specific NADPH oxidase inhibitor or gene knockdown lead to impaired ROS production and subsequent inhibition of pollen germination and pollen tube growth.
Highlights
Pollen–pistil interaction is recognized as a key aspect of sexual plant reproduction
Considering that superoxide (O2−) generation in mature pollen is described as mainly produced by the physiological activity of NADPH oxidases (Potocky et al, 2007); we decided to investigate the occurrence of NADPH oxidases in the olive (O. europaea L.) tree
We have carried out a complex characterization of a superoxide-producing respiratory burst oxidase homologs” (Rbohs)-homologous protein from olive pollen (OeRbohH), which allowed us to identify it as a key protein involved in both pollen germination and pollen tube growth
Summary
Pollen–pistil interaction is recognized as a key aspect of sexual plant reproduction. The pollen grains must undergo a tightly controlled sequence of physiological events after landing on compatible stigmatic papillae These processes involve the initial pollen rehydration and germination, the pollen tube growth through the female tissues, and the final interaction with the embryo sac to eventually achieve the double fertilization and generate the progeny. NADPH oxidase enzymes are eukaryotic proteins able to catalyze the physiological generation of the short-lived superoxide radical (O2−) throughout membranes (Lambeth, 2004), which is rapidly dismutated leading to H2O2 accumulation (Lamb and Dixon, 1997). This protein family shares six transmembrane central domains, two heme-binding sites, and a long cytoplasmic C-terminal end owning FAD- and NADPH-binding domains. In Arabidopsis thaliana, 10 NADPH oxidase homologues are encoded (Torres et al, 1998; Dangl and Jones, 2001), which are designed as “respiratory burst oxidase homologs” (Rbohs)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
