Čeština
EnglishAntagonistic roles of abscisic acid and cytokinin during response to nitrogen depletion in oleaginous microalga Nannochloropsis oceanica expand the evolutionary breadth of phytohormone function
Lu Y., Tarkowská D., Turečková V., Luo T., Xin Y, Li J, Wang Q, Jiao N., Strnad M., Xu J.
PLANT JOURNAL 80: 52-68, 2014
Keywords: Nannochloropsis oceanica, antagonistic synergy between abscisic acid and cytokinin, phytohormone evolution, stress response, cell cycle progression
Abstract: The origin of phytohormones is poorly understood and their physiological roles in microalgae remain elusive. Genome comparison of photosynthetic autotrophic eukaryotes revealed that biosynthetic pathways of abscisic acid (ABA) and cytokinin (CK) emerged in unicellular algae. While ABA and CK degradation mechanism emerged phylogenetically broadly in microalgae, complete vascular-plant-type conjugation pathways emerged prior to the rise of Streptophyta. In microalgae, a complete set of proteins from the canonical ABA and CK sensing and signaling pathways is not essential yet individual components have emerged, suggesting a stepwise recruitment of phytohormone signaling components. In an oleaginous Eustigmatophyte Nannochloropsis oceanica IMET1, ultra-high performance liquid chromatography electrospray ionisation tandem mass spectrometry detected a wide array of plant hormones, despite a phytohormone profile highly distinct from flowering plants. Time-series transcriptional analysis during nitrogen-depletion revealed activation of ABA biosynthetic pathway and antagonistic transcription of CK biosynthetic genes. Correspondingly, the ABA level increases while the dominant bioactive CK forms decrease. Moreover, exogenous CKs stimulate cell cycle progression while exogenous ABA acts as both an algal growth repressor and a positive regulator in response to stresses. The presence of such functional flowering plant-like phytohormone signaling systems in Nannochloropsis sp. suggests a much earlier origin of phytohormone biosynthesis and degradation than previously believed, and supports the presence in microalgae of as-yet unknown conjugation and sensing-signaling systems that may be exploited for microalgal feedstock development.
DOI: 10.1111/tpj.12615 IEB authors: Miroslav Strnad, Danuše Tarkowská
PLANT JOURNAL 80: 52-68, 2014
Keywords: Nannochloropsis oceanica, antagonistic synergy between abscisic acid and cytokinin, phytohormone evolution, stress response, cell cycle progression
Abstract: The origin of phytohormones is poorly understood and their physiological roles in microalgae remain elusive. Genome comparison of photosynthetic autotrophic eukaryotes revealed that biosynthetic pathways of abscisic acid (ABA) and cytokinin (CK) emerged in unicellular algae. While ABA and CK degradation mechanism emerged phylogenetically broadly in microalgae, complete vascular-plant-type conjugation pathways emerged prior to the rise of Streptophyta. In microalgae, a complete set of proteins from the canonical ABA and CK sensing and signaling pathways is not essential yet individual components have emerged, suggesting a stepwise recruitment of phytohormone signaling components. In an oleaginous Eustigmatophyte Nannochloropsis oceanica IMET1, ultra-high performance liquid chromatography electrospray ionisation tandem mass spectrometry detected a wide array of plant hormones, despite a phytohormone profile highly distinct from flowering plants. Time-series transcriptional analysis during nitrogen-depletion revealed activation of ABA biosynthetic pathway and antagonistic transcription of CK biosynthetic genes. Correspondingly, the ABA level increases while the dominant bioactive CK forms decrease. Moreover, exogenous CKs stimulate cell cycle progression while exogenous ABA acts as both an algal growth repressor and a positive regulator in response to stresses. The presence of such functional flowering plant-like phytohormone signaling systems in Nannochloropsis sp. suggests a much earlier origin of phytohormone biosynthesis and degradation than previously believed, and supports the presence in microalgae of as-yet unknown conjugation and sensing-signaling systems that may be exploited for microalgal feedstock development.
DOI: 10.1111/tpj.12615 IEB authors: Miroslav Strnad, Danuše Tarkowská