Mitochondria Change Dynamics and Morphology during Grapevine Leaf Senescence

Abstract

Leaf senescence is the last stage of development of an organ and is aimed to its ordered disassembly and nutrient reallocation. Whereas chlorophyll gradually degrades during senescence in leaves, mitochondria need to maintain active to sustain the energy demands of senescing cells. Here we analysed the motility and morphology of mitochondria in different stages of senescence in leaves of grapevine (Vitis vinifera), by stably expressing a GFP (green fluorescent protein) reporter targeted to these organelles. Results show that mitochondria were less dynamic and markedly changed morphology during senescence, passing from the elongated, branched structures found in mature leaves to enlarged and sparse organelles in senescent leaves. Progression of senescence in leaves was not synchronous, since changes in mitochondria from stomata were delayed. Mitochondrial morphology was also analysed in grapevine cell cultures. Mitochondria from cells at the end of their growth curve resembled those from senescing leaves, suggesting that cell cultures might represent a useful model system for senescence. Additionally, senescence-associated mitochondrial changes were observed in plants treated with high concentrations of cytokinins. Overall, morphology and dynamics of mitochondria might represent a reliable senescence marker for plant cells.

Dissecting the Metabolic Role of Mitochondria during Developmental Leaf Senescence

“…S1C). These data about the mitochondrial population corroborate earlier studies obtained with Arabidopsis undergoing dark-induced leaf senescence (Keech et al, 2007) and DLS (Keech 2011) as well as with grapevine leaves undergoing DLS (Ruberti et al, 2014). In a second step, electron microscopy was carried out to better visualize the ultrastructural changes occurring in organelles in mesophyll cells ( Fig.…”

“…Surprisingly, the role played by mitochondria during DLS appears poorly documented, even though a thorough understanding of the major cellular players involved is crucial in the optimization and management of this process. A number of studies, however, have put forward some interesting observations in Medicago truncatula cells (Zottini et al, 2006), Arabidopsis (Arabidopsis thaliana; Keech et al, 2007;Keech, 2011;Woo et al, 2016), grapevine (Vitis vinifera; Ruberti et al, 2014), and poplar (Populus spp. ; Bhalerao et al, 2003;Keskitalo et al, 2005), revealing the persistent presence of mitochondria in the cell, long after the chloroplasts have commenced disassembly and whole-cell metabolism has been thoroughly modified.…”

Fission and Fusion of Plant Mitochondria, and Genome Maintenance

“…During leaf senescence in individually darkened leaves in Arabidopsis, the number of mitochondria decreases (Keech et al, 2007), probably by autophagy . The remaining mitochondria retain their motility and respiration activity until the last step of leaf senescence (Keech et al, 2007;Keech, 2011;Ruberti et al, 2014;Chrobok et al, 2016). These mitochondria are thought to provide energy and metabolites for degrading the cell components and relocating them to other younger parts of the plant (Keech et al, 2007;Keech, 2011;Ruberti et al, 2014;Chrobok et al, 2016).…”

Mitochondrial outer membrane forms bridge between two mitochondria in Arabidopsis thaliana

“…3,4 In particular, plant mitochondria are more spherical than animal mitochondria and their morphology depends on the developmental stage and growth conditions. [5][6][7][8] In previous works, plant mitochondrial morphology and dynamics were usually studied by staining the matrix with a fluorescent dye or by visualizing fluorescently-labeled proteins in the matrix. 5,6,8 As a result, the behavior of the mitochondrial outer membrane has received little attention.…”

“…[5][6][7][8] In previous works, plant mitochondrial morphology and dynamics were usually studied by staining the matrix with a fluorescent dye or by visualizing fluorescently-labeled proteins in the matrix. 5,6,8 As a result, the behavior of the mitochondrial outer membrane has received little attention. As the outermost layer of mitochondria, the mitochondrial outer membrane mediates the import of proteins and lipids, the passage of small molecules and conduction of signaling events between the mitochondrion and the cytosol.…”