Figure 1.Induction of ROS production in Arabidopsis guard cells’ chloroplasts by ABA and MJ. (A) Leaf disks were prepared from wild-type plants and treated with ABA and MJ. After incubation of leaf discs in solution with the phytohormones, cells were loaded with H2DCFDA as described in methods. Shown are representative images of single section confocal microscopy (1 μm thick) of guard cells from the different treatments. Scale bar = 10 µm. (B) Quantification of the H2DCFDA-dependent fluorescence of individual chloroplasts shown in (A). Quantification was done using ImagePRO-Plus program from projected images of 2–3 confocal Z stack sections of individual chloroplasts, as described in methods. Shown is a representative one of three replicate experiments. n = 30 chloroplasts from 10 guard cells sampled from three different young rosette leaves (± SE). R.U. relative unites.
Zooming into sub-organellar localization of reactive oxygen species in guard cell chloroplasts during abscisic acid and methyl jasmonate treatments
Leshem Y., Levine A. (2013)
Plant Signal Behav. 8(10): – doi: 10.4161/psb.25689 – PMID: 23887496 – PMCID: PMC4091116 –
Regulation of stomata movements is crucial for plants ability to cope with their changing environment. Guard cells’ (GC) water potential directs water flux inside/outside this cell, which eventually is causing the stoma to open or close, respectively. Some of the osmolytes which accumulates in the GC cytoplasm and are known to play a role in stomata opening are sugars, arising from chloroplast starch degradation. During stomata closure, the accumulated osmolytes are removed from the GC cytoplasm. Surprisingly little is known about prevention of starch degradation and forming additional sugars which may interfere with osmotic changes that are necessary for correct closure of stomata.
One of the early events leading to stomata closure is production of reactive oxygen species (ROS) in various subcellular sites and organelles of the stoma. Here we report that ROS production during abscisic acid (ABA) and methyl jasmonate (MJ) stimuli in Arabidopsis GC chloroplasts were more than tripled. Moreover, ROS were detected on the suborganelle level in compartments that are typically occupied by starch grains. This observation leads us to suspect that ROS function in that particular location is necessary for stomata closure. We therefore hypothesize that these ROS are involved in redox control that lead to the inactivation of starch degradation that takes place in these compartments, thus contributing to the stoma closure in an additional way.
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