Lesson 5 - Structure_ Peroxisome & Plastids PDF

Primer Question Why does a plant cell need both plastids/chloroplasts & mitochondria?  Structure: Peroxisomes, & Plastids Peroxisomes Plastid Introduction Plastid Types & Interconversion Plastid Replication & Inheritance Plastid Genome Peroxisomes: Handling Hazardous...

Primer Question Why does a plant cell need both plastids/chloroplasts & mitochondria?  Structure: Peroxisomes, & Plastids Peroxisomes Plastid Introduction Plastid Types & Interconversion Plastid Replication & Inheritance Plastid Genome Peroxisomes: Handling Hazardous Work Membrane bound organelle handling oxidative metabolism ○ Lipid metabolism ○ Produces, scavenges, & degrades hydrogen peroxide Often closely associated with chloroplasts, mitochondria, & the ER Does not contain DNA!  Plastid Introduction: Special Semi-Autonomous Factories Beloved powerhouses of the plant cell Critical roles in energy production & metabolism Unique among organelles for having their own DNA & replication processes Plastid Introduction: Special Semi-Autonomous Factories Archaea ancestor begins to develop an The Endosymbiotic Origin Theory endomembrane system 1. An archaea ancestor engulfed a prokaryotic cell without digestion 2. The engulfed prokaryote retained function & ability to replicate, passing down to the host cell’s offspring 3. Over time these prokaryotes “off-loaded” elements of their genome to the host cell & specializing into the powerhouses we know today Plastid Introduction: Special Semi-Autonomous Factories  Plastid Types & Interconversion Plastids can specialize into many roles All types can interconvert into another given the appropriate conditions The plastid type within a cell typically reflects the cell’s identity & function  Plastid Types & Interconversion Proplastid Precursor to all other plastid types Found in the least differentiated tissues (i.e. meristem, gametes) Solymosi et al., 2018. Methods in Molecular Biology, vol 1829. DOI: 10.1007/978-1-4939-8654-5_4  Plastid Types & Interconversion Leucoplast Colorless, non-pigmented plastids ○ Lack thylakoids Overarching classification for three sub-types Solymosi et al., 2018. Methods in Molecular Biology, vol 1829. DOI: 10.1007/978-1-4939-8654-5_4 Plastid Types & Interconversion Amyloplast - “Starch Sink” Starch synthesis & storage Found in storage tissues like tubers & roots Can have gravity-sensing function in root cap cells Solymosi et al., 2018. Methods in Molecular Biology, vol 1829. DOI: 10.1007/978-1-4939-8654-5_4 Plastid Types & Interconversion Elaioplast - “Fat Factory” Synthesis & storage of fatty acids, terpenes, & other lipids Found in seeds, anthers, & fruit peels Solymosi et al., 2018. Methods in Molecular Biology, vol 1829. DOI: 10.1007/978-1-4939-8654-5_4 Plastid Types & Interconversion Proteinoplast - “Protein Pocket” Synthesis & storage of large bodies of proteins Found in storage tissues, especially seeds Solymosi et al., 2018. Methods in Molecular Biology, vol 1829. DOI: 10.1007/978-1-4939-8654-5_4 Plastid Types & Interconversion Chromoplast - “Color Captain” Stores mostly non-polar pigments ○ Esp. red, orange, & yellow Found in fruits, tubers, & flowers Solymosi et al., 2018. Methods in Molecular Biology, vol 1829. DOI: 10.1007/978-1-4939-8654-5_4  Plastid Types & Interconversion Etioplast - “Standby Solar Plant” Precursor to chloroplasts when light is unavailable Found during early germination or in tissues grown in the dark Solymosi & Aronsson, 2013. DOI: 10.1007/978-94-007-5724-0_3 Solymosi et al., 2018. Methods in Molecular Biology, vol 1829. DOI: 10.1007/978-1-4939-8654-5_4 Plastid Types & Interconversion Chloroplast - “Solar Powerhouse” The critical site of light-harvesting & photosynthesis Found in green tissues Most complex plastid type Solymosi et al., 2018. Methods in Molecular Biology, vol 1829. DOI: 10.1007/978-1-4939-8654-5_4 Plastid Types & Interconversion Examples of Interconversion Chloroplast >>>> Chromoplast Amyloplast >>>> Chloroplast Review Q break The _____ is the plastid type responsible for storing starch ______ are plastid types without pigments or thylakoids. Instead they create &/or store different types of nutrients T/F A proplastid can only become one type of plastid during its lifetime Plastid Replication: Semi-Autonomous Factories Can’t be made by the plant cell Replicate thru division of existing plastids Inherited from parent to offspring All plastid types divide to keep pace with cell division, metabolic needs, & environmental cues Divide by binary fission - like bacteria DNA replication, transcription, & translation also mirror prokaryotes Yoshida, 2018. DOI: 10.3390/ijms19030733  We need Plastid Genome: A skeleton crew more small Rubisco subunits! “Circular” genome structured like bacteria, but much smaller Plastid = < 2000 kbp :: E. coli = 4-6Mb Majority of the genome has transferred to the nucleus via horizontal gene transfer Only encodes some proteins & RNA for essential processes Regulation & signaling Ribosomes Some photosynthetic machinery de Vries & Archibald, 2018. DOI: 10.1016/j.cub.2018.01.027 Plastid Genome - Nuclear Interactions Necessary for proper regulation of plastid-related gene expression & development Since the involved genes are split between them, multiple different signal feedback loops & transfer of proteins coordinate nuclear & plastid activity Nucleus Chloroplast Plastid Genome - Nuclear Interactions Necessary for proper regulation of plastid-related gene expression & development Since the involved genes are split between them, multiple different signal feedback loops & transfer of proteins coordinate nuclear & plastid activity Photosynthesis Protein Example Small subunits of Rubisco - the enzyme central to photosynthesis - are made in the cytosol & imported into the chloroplast. Large subunits are made in the chloroplast  Plastid Genome - Nuclear Interactions Necessary for proper regulation of plastid-related gene expression & development Since the involved genes are split between them, multiple different signal feedback loops & transfer of proteins coordinate nuclear & plastid activity Import Protein Example Mutants in plastid import proteins can have pale phenotypes with reduced growth, due to improper signaling & plastid development Loudya et al, 2020. 10.1098/rstb.2019.0400 Plastid Genome - Nuclear Interactions Necessary for proper regulation of plastid-related gene expression & development Since the involved genes are split between them, multiple different signal feedback loops & transfer of proteins coordinate nuclear & plastid activity Biosynthesis Monitoring Example Genome UNcoupled (GUN) genes are often involved in different steps of chlorophyll biosynthesis.This shows biosynthetic intermediates themselves are important signals  Plastid Genome - Nuclear Interactions Necessary for proper regulation of plastid-related gene expression & development Since the involved genes are split between them, multiple different signal feedback loops & transfer of proteins coordinate nuclear & plastid activity Biosynthesis Monitoring Example Results of reduction & oxidation (redox) reactions, like reactive oxygen species (ROS) are important signals.They communicate the levels of stress photosynthetic & other biochemical machinery is under Leister, 2019. DOI: 10.1089/ars.2017.7392 Plastid Genome - Nuclear Interactions Necessary for proper regulation of plastid-related gene expression & development Since the involved genes are split between them, multiple different signal feedback loops & transfer of proteins coordinate nuclear & plastid activity We’ll cover plastid import/export & signaling with more detail later in the semester. For now, this helps illustrate some of the many ways signals can exist & move within the cell. My next section will cover important signaling principles through detailing a few fundamental systems plant cells use to bring signals from the cell surface into the cytoplasm.  REMINDER Quiz 1 will take place on bCourses in-class this coming Monday (2/3) You can bring one A4 sized paper with handwritten notes as a “cheat sheet” If you haven’t communicated DSP accommodations please do so ASAP Review Q’s T/F Plastids cannot be made by the cell & have their own separate processes for division & replication that aren’t necessarily coordinated with plant cell division. T/F Only chloroplasts can exchange signals with the nucleus Plastids require communication with the nucleus for proper function.Which of the following statements is FALSE? - Intermediates in chlorophyll biosynthesis can be used as developmental signals - All proteins found in a plastid are coded in the nucleus & must be imported from the cytosol - Redox signals are important for indicating the stress levels of various plastid machinery & coordinating repair & stress-avoidance responses