Mitochondrial dysfunction affects chloroplast functions

Abstract

Plants require the contribution of three different genomes found in separate compartments. Chloroplasts and mitochondria, which are of endosymbiotic origin, contain only relatively few proteins encoded by their own genomes, following the transfer of a great part of the genetic material from the prokaryotic ancestors into the nucleus of the host. Consequently, most of the mitochondrial and chloroplast proteins are nuclear-encoded, synthesized in the cytoplasm and imported into organelles. [1][2][3] Given that several cellular functions are performed by proteins encoded in different compartments, the existence of mechanisms that coordinate the expression of nuclear and organellar genes should be necessary. One important question concerns the character (identity) of the signals responsible for interorganellar cross-talk able to direct the expression of a set of nuclear genes.The intercompartment cross-talk includes anterograde (nucleus-to-organelle) and retrograde (organelle-to-nucleus) controls. Anterograde mechanisms are responsive to endogenous and environmental signals received by the kernel and coordinate the expression of genes in chloroplasts and mitochondria. Retrograde signaling regulates the expression of nuclear genes in response to the physiological state of organelles. Besides the cross-talk between chloroplasts/mitochondria and nucleus, interactions between chloroplast and mitochondria has been established during the evolution of plants to coordinate the activities of the two organelles which exhibit a high degree of metabolic independence 4 ( Fig. 1). Profound changes in gene expression of nuclear-encoded genes were observed in Arabidopsis plants exhibiting impaired mitochondrial function. [5][6][7][8][9][10][11][12] The recent study of the transcriptomeThe transcriptomic response of A9:u-ATP9 and apetala3:u-ATP9 lines carrying a mitochondrial dysfunction in flower tissues has been characterized. Both lines showed an alteration in the transcription of several genes involved in carbon and nitrogen metabolism, stress responses, transcription factors and DNA binding proteins. Interestingly, several transcripts of photosynthetic-related genes were also affected in their expression such as the mRNAs encoding for chlorophyllase, chlorophyll binding proteins and a PSII. Moreover, chlorophyll levels were reduced and the Mg-dechelatase activity was increased, indicating an alteration in chlorophyll metabolism. Our results suggest that the mitochondrial dysfunction may also affect chloroplastic functions, and that our model could be useful to uncover retrograde signaling mechanisms operating between the three different plant genomes. Keywords: mitochondria, chloroplasts, mitochondrial dysfunction, arabidopsis in Arabidopsis plants carrying a mitochondrial dysfunction, revealed important modifications in the expression of some genes from the carbon metabolic pathways with inhibition of glycolysis and the induction of the MDH alternative pathways. Mitochondrial dysfunction affects chloroplast functions 13This mo...

Mitochondria and chloroplasts function in microalgae energy production

“…Various works have shown that the mitochondria have a key role in the provision of cellular energy, as well as in the participation in retrograde regulation mechanisms involved in the biogenesis of other organelles ( i.e. , chloroplasts) in plants and algae ( Busi et al, 2011 ; Liu & Butow, 2006 ; Liu et al, 2018 ). Although mitochondria and chloroplasts were traditionally considered as autonomous compartments, there is much evidence that the crosstalk between these organelles directly impacts on cell physiology ( Raghavendra & Padmasree, 2003 ).…”

“…Although mitochondria and chloroplasts were traditionally considered as autonomous compartments, there is much evidence that the crosstalk between these organelles directly impacts on cell physiology ( Raghavendra & Padmasree, 2003 ). For example, mitochondrial metabolism, particularly the bioenergetic reactions of oxidative electron transport and phosphorylation are still active in the light and are essential for maintain photosynthetic carbon assimilation ( Busi et al, 2011 ; Raghavendra & Padmasree, 2003 ).…”