plant evolution

Differences between plant and animal physiology and reproduction cause minor differences in how they evolve.

One major difference is the totipotent nature of plant cells, allowing them to reproduce asexually much more easily than most animals. They are also capable of polyploidy – where more than two chromosome sets are inherited from the parents. This allows relatively fast bursts of evolution to occur, for example by the effect of gene duplication. The long periods of dormancy that seed plants can employ also makes them less vulnerable to extinction, as they can "sit out" the tough periods and wait until more clement times to leap back to life.{{Cite journal |last1=Willis |first1=Charles G. |last2=Baskin |first2=Carol C. |last3=Baskin |first3=Jerry M. |last4=Auld |first4=Josh R. |last5=Venable |first5=D. Lawrence |last6=Cavender-Bares |first6=Jeannine |last7=Donohue |first7=Kathleen |last8=Rubio de Casas |first8=Rafael |last9=The NESCent Germination Working Group |date=July 2014 |title=The evolution of seed dormancy: environmental cues, evolutionary hubs, and diversification of the seed plants |journal=New Phytologist |language=en |volume=203 |issue=1 |pages=300–309 |doi=10.1111/nph.12782 |pmid=24684268 |issn=0028-646X|doi-access=free }}

The effect of these differences is most profoundly seen during extinction events. These events, which wiped out between 6 and 62% of terrestrial animal families, had "negligible" effect on plant families.{{cite journal

| author = McElwain, J.C.

|author2=Punyasena, S.W.

| year = 2007

| title = Mass extinction events and the plant fossil record

| journal = Trends in Ecology & Evolution

| pmid = 17919771

| volume = 22

| issue = 10

| pages = 548–557

| doi=10.1016/j.tree.2007.09.003

}} However, the ecosystem structure is significantly rearranged, with the abundances and distributions of different groups of plants changing profoundly. These effects are perhaps due to the higher diversity within families, as extinction – which was common at the species level – was very selective. For example, wind-pollinated species survived better than insect-pollinated taxa, and specialised species generally lost out. In general, the surviving taxa were rare before the extinction, suggesting that they were generalists who were poor competitors when times were easy, but prospered when specialised groups became extinct and left ecological niches vacant.

During embryogenesis, plants and animals pass through a phylotypic stage that evolved independently{{Cite journal|last1=Drost|first1=Hajk-Georg|last2=Janitza|first2=Philipp |last3=Grosse |first3=Ivo |last4=Quint |first4=Marcel | year=2017|title=Cross-kingdom comparison of the developmental hourglass|journal=Current Opinion in Genetics & Development|volume=45|pages=69–75|doi=10.1016/j.gde.2017.03.003|pmid=28347942|doi-access=free}} and that causes a developmental constraint limiting morphological diversification.{{Cite journal|last1=Irie|first1=Naoki|last2=Kuratani|first2=Shigeru|date=2011-03-22|title=Comparative transcriptome analysis reveals vertebrate phylotypic period during organogenesis|journal=Nature Communications|language=en|volume=2|doi=10.1038/ncomms1248|issn=2041-1723|pmc=3109953|pmid=21427719|pages=248|bibcode=2011NatCo...2..248I}}{{Cite journal|last1=Domazet-Lošo|first1=Tomislav|last2=Tautz|first2=Diethard|date=2010-12-09|title=A phylogenetically based transcriptome age index mirrors ontogenetic divergence patterns|journal=Nature|language=en|volume=468|issue=7325|pages=815–818|doi=10.1038/nature09632|issn=0028-0836|pmid=21150997|bibcode=2010Natur.468..815D|s2cid=1417664}}{{Cite journal|last1=Quint|first1=Marcel|last2=Drost|first2=Hajk-Georg|last3=Gabel|first3=Alexander|last4=Ullrich|first4=Kristian Karsten|last5=Bönn|first5=Markus|last6=Grosse|first6=Ivo|date=2012-10-04|title=A transcriptomic hourglass in plant embryogenesis|journal=Nature|language=en|volume=490|issue=7418|pages=98–101|doi=10.1038/nature11394|pmid=22951968|bibcode=2012Natur.490...98Q|s2cid=4404460|issn=0028-0836}}{{Cite journal|last1=Drost|first1=Hajk-Georg|last2=Gabel|first2=Alexander|last3=Grosse|first3=Ivo|last4=Quint|first4=Marcel|date=2015-05-01|title=Evidence for Active Maintenance of Phylotranscriptomic Hourglass Patterns in Animal and Plant Embryogenesis|url= |journal=Molecular Biology and Evolution|language=en|volume=32|issue=5|pages=1221–1231|doi=10.1093/molbev/msv012|issn=0737-4038|pmc=4408408|pmid=25631928}}

File:Polyploidization.svg cell undergoes failed meiosis, producing diploid gametes, which self-fertilize to produce a tetraploid zygote.]]

Polyploidy is pervasive in plants and some estimates suggest that 30–80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes.{{cite journal |vauthors=Meyers LA, Levin DA | title = On the abundance of polyploids in flowering plants | journal = Evolution | volume = 60 | issue = 6 | pages = 1198–206 |date=June 2006 | pmid = 16892970 | doi = 10.1111/j.0014-3820.2006.tb01198.x | s2cid = 43039505 | doi-access = free }}{{cite journal |vauthors=Rieseberg LH, Willis JH | title = Plant speciation | journal = Science | volume = 317 | issue = 5840 | pages = 910–4 |date=August 2007 | pmid = 17702935 | pmc = 2442920 | doi = 10.1126/science.1137729 | bibcode = 2007Sci...317..910R }}{{cite journal | author = Otto SP | title = The evolutionary consequences of polyploidy | journal = Cell | volume = 131 | issue = 3 | pages = 452–62 |date=November 2007 | pmid = 17981114 | doi = 10.1016/j.cell.2007.10.022 | s2cid = 10054182 | doi-access = free }} Huge explosions in angiosperm species diversity appear to have coincided with ancient genome duplications shared by many species.de Bodt et al. 2005 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase.{{cite journal |vauthors=Wood TE, Takebayashi N, Barker MS, Mayrose I, Greenspoon PB, Rieseberg LH | title = The frequency of polyploid speciation in vascular plants | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 106 | issue = 33 | pages = 13875–9 |date=August 2009 | pmid = 19667210 | pmc = 2728988 | doi = 10.1073/pnas.0811575106 | bibcode = 2009PNAS..10613875W | doi-access = free }} Most polyploids display heterosis relative to their parental species, and may display novel variation or morphologies that may contribute to the processes of speciation and eco-niche exploitation.{{cite journal | author = Comai L | title = The advantages and disadvantages of being polyploid | journal = Nat. Rev. Genet. | volume = 6 | issue = 11 | pages = 836–46 |date=November 2005 | pmid = 16304599 | doi = 10.1038/nrg1711 | s2cid = 3329282 }} The mechanisms leading to novel variation in newly formed allopolyploids may include gene dosage effects (resulting from more numerous copies of genome content), the reunion of divergent gene regulatory hierarchies, chromosomal rearrangements, and epigenetic remodeling, all of which affect gene content and/or expression levels.{{cite journal |vauthors=Osborn TC, Pires JC, Birchler JA, Auger DL, Chen ZJ, Lee HS, Comai L, Madlung A, Doerge RW, Colot V, Martienssen RA | title = Understanding mechanisms of novel gene expression in polyploids | journal = Trends Genet. | volume = 19 | issue = 3 | pages = 141–7 |date=March 2003 | pmid = 12615008 | doi = 10.1016/S0168-9525(03)00015-5}}{{cite journal |vauthors=Chen ZJ, Ni Z | title = Mechanisms of genomic rearrangements and gene expression changes in plant polyploids | journal = BioEssays | volume = 28 | issue = 3 | pages = 240–52 |date=March 2006 | pmid = 16479580 | pmc = 1986666 | doi = 10.1002/bies.20374 }}{{cite journal | author = Chen ZJ | title = Genetic and epigenetic mechanisms for gene expression and phenotypic variation in plant polyploids | journal = Annu Rev Plant Biol | volume = 58 | pages = 377–406 | year = 2007 | pmid = 17280525 | pmc = 1949485 | doi = 10.1146/annurev.arplant.58.032806.103835 }} Many of these rapid changes may contribute to reproductive isolation and speciation.

All eukaryotes probably have experienced a polyploidy event at some point in their evolutionary history. See paleopolyploidy. In many cases, these events can be inferred only through comparing sequenced genomes. Angiosperms have paleopolyploidy in their ancestry. Unexpected ancient genome duplications have recently been confirmed in mustard weed/thale cress (Arabidopsis thaliana) and rice (Oryza sativa).

{{Further|Photosynthesis}}

File:Plagiomnium affine laminazellen.jpeg)]]

Cyanobacteria remained principal primary producers throughout the Proterozoic Eon (2500–543 Ma), in part because the redox structure of the oceans favored photoautotrophs capable of nitrogen fixation. {{Citation needed|date=July 2008}} Green algae joined blue-greens as major primary producers on continental shelves near the end of the Proterozoic, but only with the Mesozoic (251–65 Ma) radiations of dinoflagellates, coccolithophorids, and diatoms did primary production in marine shelf waters take modern form. Cyanobacteria remain critical to marine ecosystems as primary producers in oceanic gyres, as agents of biological nitrogen fixation, and, in modified form, as the plastids of marine algae.{{cite book|author = Herrero A and Flores E (editor).|title = The Cyanobacteria: Molecular Biology, Genomics and Evolution|edition = 1st|publisher = Caister Academic Press|year = 2008| isbn = 978-1-904455-15-8}}

Chloroplasts have many similarities with cyanobacteria, including a circular chromosome, prokaryotic-type ribosomes, and similar proteins in the photosynthetic reaction center.{{cite journal |author=Douglas SE |title=Plastid evolution: origins, diversity, trends |journal=Curr. Opin. Genet. Dev. |volume=8 |issue=6 |pages=655–61 |year=1998 |pmid=9914199 |doi= 10.1016/S0959-437X(98)80033-6}}{{cite journal |vauthors=Reyes-Prieto A, Weber AP, Bhattacharya D |title=The origin and establishment of the plastid in algae and plants |journal=Annu. Rev. Genet. |volume=41 |pages=147–68 |year=2007 |pmid=17600460 |doi=10.1146/annurev.genet.41.110306.130134}} The endosymbiotic theory suggests that photosynthetic bacteria were acquired (by endocytosis) by early eukaryotic cells to form the first plant cells. Therefore, chloroplasts may be photosynthetic bacteria that adapted to life inside plant cells. Like mitochondria, chloroplasts still possess their own DNA, separate from the nuclear DNA of their plant host cells and the genes in this chloroplast DNA resemble those in cyanobacteria.{{cite journal |vauthors=Raven JA, Allen JF |title=Genomics and chloroplast evolution: what did cyanobacteria do for plants? |journal=Genome Biol. |volume=4 |issue=3 |page=209 |year=2003 |pmid=12620099 |pmc=153454 |doi=10.1186/gb-2003-4-3-209 |doi-access=free }} DNA in chloroplasts codes for redox proteins such as photosynthetic reaction centers. The CoRR hypothesis proposes that this Co-location is required for Redox Regulation.

Transcription factors and transcriptional regulatory networks play key roles in plant development and stress responses, as well as their evolution. During plant landing, many novel transcription factor families emerged and are preferentially wired into the networks of multicellular development, reproduction, and organ development, contributing to more complex morphogenesis of land plants.{{cite journal |last1=Jin JP|display-authors=etal| title= An Arabidopsis transcriptional regulatory map reveals distinct functional and evolutionary features of novel transcription factors|journal= Molecular Biology and Evolution | date=July 2015 |volume=32 |issue=7|doi=10.1093/molbev/msv058 |url= |pmid=25750178 |pmc=4476157 |pages=1767–1773}}

Charles Darwin in his 1878 book The Effects of Cross and Self-Fertilization in the Vegetable KingdomDarwin, C. R. 1878. The effects of cross and self fertilisation in the vegetable kingdom. London: John Murray". darwin-online.org.uk at the beginning of chapter XII noted “The first and most important of the conclusions which may be drawn from the observations given in this volume, is that generally cross-fertilisation is beneficial and self-fertilisation often injurious, at least with the plants on which I experimented.” Flowers emerged in plant evolution as an adaptation for the promotion of cross-fertilisation (outcrossing), a process that allows the masking of deleterious mutations in the genome of progeny. The genetic masking effect of cross-fertilisation sexual reproduction is known as genetic complementation.Bernstein H, Byerly HC, Hopf FA, Michod RE. Genetic damage, mutation, and the evolution of sex. Science. 1985 Sep 20;229(4719):1277-81. doi: 10.1126/science.3898363. PMID: 3898363 This beneficial effect of cross-fertilisation on progeny is also recognized as hybrid vigor or heterosis. Once flowers became established as an evolutionary adaptation to promote cross-fertilization, subsequent switching to inbreeding ordinarily becomes disadvantageous, largely because it allows expression of the previously masked deleterious recessive mutations, i.e. inbreeding depression.

• Evolutionary history of plants
• Annual vs. perennial plant evolution

• [https://www.britannica.com/plant/plant/Evolution-of-seed-plants-and-plant-communities Evolution And Paleobotany] at [https://www.britannica.com/ Britannica]

Category:Evolution of plants