492 / 2019-02-28 14:34:24

How Arabidopsis chloroplasts maintain energy efficiency during the day and the night

ATP,reducing consumption and saving energy,chloroplasts,mitochondria,NADPH

全体主题 > Photosynthesis

Mesophyll chloroplasts generate energy under illumination but consume energy in the dark. How could chloroplasts maximize its energy harvest during the day but minimize its energy consumption at night? That ATP can be translocated into and out of mature plant chloroplasts was first reported in 1969 (Heldt 1969). Since then, it has been suggested that cytosolic ATP can enter chloroplasts to fulfil its nocturnal energy demand (Reinhold et al. 2007; Facchinelli and Weber 2011; Flügge et al. 2011). Here, by monitoring changes in ATP levels in the plastids and cytosol of live plants using a MgATP2- specific Förster resonance energy transfer (FRET)-based sensor, chloroplasts were shown to consume a large amount of ATP in the dark, and cytosolic ATP can only enter immature chloroplasts to support their biogenesis but ATP import to mature chloroplasts was negligible. Employing a combination of photosynthetic and respiratory inhibitors we corroborate the dependency of stromal ATP production on mitochondrial activity. Our findings have strong implications on how chloroplasts obtain ATP at night, how chloroplasts balance its ATP/NADPH demand and supply, and how important the role of mitochondria in dissipating surplus reducing equivalents during photosynthesis. We shall illustrate how efficient cooperation between chloroplasts and mitochondria can boost photosynthetic activity, ATP production, sucrose synthesis, plant growth and seed yield of a transgenic Arabidopsis line.