Plant Development: Cell Differentiation 2024-2025 PDF

Bases moleculares del desarrollo vegetal Tema 1. Crecimiento y diferenciación celular ▪ Ciclo de vida de las plantas: alternancia de generaciones ▪ Ciclo celular y desarrollo ▪ Determinación celular ▪ Diferenciación celular y crecimiento ▪ Organogénesis y morfogénesis ...

Bases moleculares del desarrollo vegetal Tema 1. Crecimiento y diferenciación celular ▪ Ciclo de vida de las plantas: alternancia de generaciones ▪ Ciclo celular y desarrollo ▪ Determinación celular ▪ Diferenciación celular y crecimiento ▪ Organogénesis y morfogénesis Bases moleculares del desarrollo vegetal Sequence of evolutionary and developmental innovations Cladogram showing the evolutionary relationships among the various members of the plants and their close relatives, the algae (Mya = million years ago) Bases moleculares del desarrollo vegetal ▪ Unlike animals, plants alternate two distinct multicellular generations to complete their life cycle: alternation of generations ▪ Products of meiosis in diploid plants are spores, and hence, diploid plant forms are so called sporophytes (2N) ▪ Each spore undergoes mitosis to form the haploid gametophyte (N) Bases moleculares del desarrollo vegetal ▪ Flowers are specialized structures of the sporophyte generation housing the reproductive development of superior plants. They can be unisexual or hermaphrodites, depending on they develop separate male and female gametophytes, or both together. ▪ Sporophyte generation in the seed plants, gymnosperms and angiosperms, is dominant and gives rise to different spores: - megaspores, which develop into the female gametophyte - microspores, which develop into the male gametophyte Bases moleculares del desarrollo vegetal ▪ Haploid female gametophyte is a multicellular structure that produces the gamete cell (egg cell), and several accompayining cells, all generated by simple mitosis (whereas haploid gametes in animals are directly produced by meiosis): gametophyte = 8-nucleate embryo sac = 2 synergids + 2 embryo sac, antipodals + 2 polar nuclei + central cell + composed by 8 cells egg cell Bases moleculares del desarrollo vegetal ▪ Haploid male gametophyte is a multicellular structure that produces two sperm nuclei and a generative nucleus, by simple mitosis (whereas haploid gametes in animals are directly produced by meiosis): gametophyte = pollen, which produces 2 sperm nuclei + generative nucleus ▪ Double fertilization: zygote (2N) + endosperm (3N) Bases moleculares del desarrollo vegetal Plant architecture ▪ Shoot apical meristem (SAM) ▪ Axillary bud meristems ▪ Root meristem ▪ Stem Shoots: nodes ▪ Leaves and internodes ▪ Root Schematic representation of the body of a typical eudicot Bases moleculares del desarrollo vegetal Shoot apex Young leaf Axillary meristem Bases moleculares del desarrollo vegetal Leaf anatomy Bases moleculares del desarrollo vegetal Stem tissues Bases moleculares del desarrollo vegetal Root apex Bases moleculares del desarrollo vegetal Root tissues Bases moleculares del desarrollo vegetal Cell wall and plasmodesmata Bases moleculares del desarrollo vegetal Plant cell anatomy ▪ Plasma membrane (or plasmalema) ▪ Cytoplasm: organelles and cytokeleton suspended within the cytosol ▪ Cytosol: water-soluble and coloidal phase, residing within the plasma membrane, but which excludes the nucleoplasm (the internal compartment of the membrane-bounded nucleus in eucaryotes) Bases moleculares del desarrollo vegetal Plant cell anatomy ▪ Cell wall: the rigid, cellulosic most-external membrane, which is exclusive of plant cells ▪ Primary (young cells) and secondary (adult cell, lignified) cell walls ▪ Middle lamella joints neighbor cells ▪ Plasmodesmata facilitate ▪ Plant cell organalles and their free movement of functions molecules between cells ▪ The nucleus Bases moleculares del desarrollo vegetal Plant cell types ▪ Dermal tissues: cover the surfaces of plants Epidermal cells Trichomes Stomata cells Bases moleculares del desarrollo vegetal Plant cell types ▪ Ground tissues from the bodies of plants In leaves, there are palisade mesophyll and a spongy mesophyll Chloroplast Mitochondria Bases moleculares del desarrollo vegetal Plant cell types ▪ Ground tissues from the bodies of plants In leaves, there are palisade mesophyll and a spongy mesophyll Peroxisomas Endoplasmic (green) and reticulum chloroplasts (red) Bases moleculares del desarrollo vegetal Plant cell types ▪ Ground tissues from the bodies of plants ✓ Under appropriate environment and endogenous conditions, mesophyll cells of the leaf can differentiate into a variety of other cell types which are in turn specific of specialized tissues. Therefore, mesophyll is considered a form of parenchyma. ✓ Parenchyma can differentiate into collenchyma: cells developed thickened primary walls although the continue to elongate (fruit pericarp, laticifers, etc.) ✓ Parenchyma can differentiate into schlerenchyma: cells showed thick secondary walls Bases moleculares del desarrollo vegetal Plant cell types ▪ Vascular tissues facilitate transport between different parts of th plant through the establisment of vascular networks ✓ Thickened secondary cell walls, perforated cell ends, and pit fields generated by the interplay of organelles involved in cell wall formation during development Bases moleculares del desarrollo vegetal Cell cycle regulation and development ▪ Cell cycle is under a strictic genetic control ▪ Check points play a relevant function in the cell cycle regulation ▪ Each phase of the cell cycle has a specific set of biochemical and cellular activities ▪ Cyclins and cyclin-dependent kinases (CDKs) are mainly involved Bases moleculares del desarrollo vegetal Plant development: cell differentiation ▪ At the beginning, plant cells are totipotent, i.e. they can be differentiated in any cell type ▪ Totipotency is lost during embryonic development and pluripotent cells are generated to Adult plants can be give rise to several cell types, but regenerated from a callus, not all of them. which is formed by ▪ Pluripotency will be restricted undifferentiated and clonal more and more until cells are cells. morphologically and physiologically distinct; they are differentiated cells Bases moleculares del desarrollo vegetal Plant development: cell differentiation and growth ▪ Cell differentiation requieres to fate to a developmental program ▪ Cell growth and proliferation are regulated by the cell cycle, endogenous (hormones) and environmental cues, and both are subjected to a precise genetic control ▪ Cell apoptosis: programmed cell death, which is essential for the development Bases moleculares del desarrollo vegetal Plant development: cell determination ▪ Cell differentiation entails that pluripotent state is restricted and finally it is lost ▪ Cell differentiation also means that a given cell commits to a developmental fate, even when this cell does not show differentiated features. At this time, cells are determinated. ▪ Cell differentiation usually involves an irreversible commitment to a developmental fate; however this fate can be reverted if position is changed in an embryonic tissue Bases moleculares del desarrollo vegetal Morfogénesis Proceso biológico que lleva a que un organismo desarrolle su forma a través de una distribución espacial organizada de sus células y tejidos