The Role of Chloroplast Localized Small Heat Shock Proteins in Singlet Oxygen Induced Chloroplast Stress

Plants are sessile organisms and thus must acclimate to changes in their surrounding environment to survive. Plants first sense these changes through alterations in photochemistry and reactive oxygen species (ROS) generation in their chloroplasts. A consequence of these alterations is the production of singlet oxygen (1O2), which then elicits a coordinated retrograde response to the nucleus to enact changes in photochemistry back in the chloroplast. Small heat shock proteins are ~100 amino acid long proteins that are currently thought to associate with unfolded proteins to prevent their degradation. Plants are the only organisms that possess organelle targeted small heat shock proteins (sHsps), but the roles of sHsps localizing to the chloroplast are not clear. To further understand the roles of these sHsps and other chloroplast protective mechanisms, we used the Arabodpsis thaliana plastid ferrochelatase 2 (fc2) mutant. Using a reverse genetics approach in the fc2 background, we have shown that chloroplast localized sHsps protect seedlings from cell death under moderate light stress, as well as protecting plants from excess light stress. Knowing how individual chloroplasts communicate and mitigate stress can not only help us further understand interorganelle signaling, but can also provide insight into photosynthetic flux and inform future improvements of crop engineering and farming practices