第1019回生物科学セミナー
Quiescence or growth? How to build organelles? Lessons from the analysis of leaf and chloroplast development by light.
Enrique Lopez-Juez（School of Biological Sciences Royal Holloway, University of London）
2014年12月04日(木) 16：00-17：30 理学部2号館323号室（第3セミナー室）
Leaves are nature’s solar panels, and chloroplasts in leaf mesophyll the corresponding solar cells. Leaves develop by proliferation and differentiation of cells at the flanks of the shoot apical meristem, where plant “stem cells” reside. Seedlings of dicot plants, like Arabidopsis thaliana, when germinated in the dark, present an arrested apical meristem and do not develop leaves, while in their pre-existing embryonic leaves (cotyledons) non-photosynthetic plastids cannot differentiate into chloroplasts. Light subsequently triggers both organ initiation and development and organelle biogenesis. To help understand how these processes take place, in the past we carried out a global gene expression analysis of the shoot apex of Arabidopsis upon first exposure from dark to light (1). A detailed examination of those data demonstrates that light acts as a rapid signal to activate coordinated cell proliferation and the overall bulk synthesis of cellular components (protein translation). They also suggest two potential regulatory mechanisms, one involving a change in hormone status brought about by light, from high auxin to high cytokinin response state, and the rapid removal of an “energy starvation” response state localised to the shoot apex. These responses can be recapitulated following dark-adaptation of early developing leaves. In addition we will present evidence for how our understanding of chloroplast development (2) is being assisted by the identification of mutations which enhance the biogenesis of these organelles in otherwise partly light-insensitive mutants.
参考文献
(1) Lopez-Juez E et al. (2008), Plant Cell 20: 947-968. PMID: 18424613
(2) Jarvis PJ and Lopez-Juez E (2013). Nat. Rev. Mol. Cell Biol. 14: 787-802. PMID: 24263360
