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{{Short description|Evolutionary history of Brassica genus}}[[File:Triangle of U Simple1.PNG|thumb|right|360px|alt=Triangle of U|The "triangle of U" diagram, showing the genetic relationships among six species of the genus ''Brassica''. Chromosomes from each of the genomes A, B and C are represented by different colours.]]
{{Short description|Evolutionary history of Brassica genus}}[[File:Triangle of U Simple1.PNG|thumb|right|360px|alt=Triangle of U|The "triangle of U" diagram, showing the genetic relationships among six species of the genus ''Brassica''. Chromosomes from each of the genomes A, B and C are represented by different colours.]]


The '''triangle of U''' ({{IPAc-en|uː}} {{respell|OO}}) is a theory about the evolution and relationships among members of the [[plant]] [[genus]] ''[[Brassica]]''. The theory states that the [[genomes]] of three ancestral [[diploid]] species of ''Brassica'' combined to create three common [[tetraploid]] [[vegetable]]s and [[Vegetable fats and oils|oilseed]] crop species.<ref name=jules2009>{{cite book |title=Plant Breeding Reviews |last=Jules |first=Janick |year=2009 |volume=31 |publisher=Wiley |isbn=978-0-470-38762-7 |page=56 |url=http://as.wiley.com/WileyCDA/WileyTitle/productCd-0470387629.html}}</ref> It has since been confirmed by studies of DNA and proteins.{{Cn|date=April 2021}}
The '''triangle of U''' ({{IPAc-en|uː}} {{respell|OO}}) is a theory about the evolution and relationships among members of the [[plant]] [[genus]] ''[[Brassica]]''. The theory states that the [[genomes]] of three ancestral [[diploid]] species of ''Brassica'' combined to create three common [[tetraploid]] [[vegetable]]s and [[Vegetable fats and oils|oilseed]] crop species.<ref name=jules2009>{{cite book |title=Plant Breeding Reviews |last=Jules |first=Janick |year=2009 |volume=31 |publisher=Wiley |isbn=978-0-470-38762-7 |page=56 |url=http://as.wiley.com/WileyCDA/WileyTitle/productCd-0470387629.html}}</ref> It has since been confirmed by studies of DNA and proteins.<ref name=pmid32595682>{{cite journal |last1=Xue |first1=JY |last2=Wang |first2=Y |last3=Chen |first3=M |last4=Dong |first4=S |last5=Shao |first5=ZQ |last6=Liu |first6=Y |title=Maternal Inheritance of U's Triangle and Evolutionary Process of <i>Brassica</i> Mitochondrial Genomes. |journal=Frontiers in plant science |date=2020 |volume=11 |pages=805 |doi=10.3389/fpls.2020.00805 |doi-access=free |pmid=32595682 |quote=Comparative genomic analyses can assign the subgenomes of the allotetraploids, B. juncea and B. napus, with their diploid parental taxa, and the results were in agreement with U’s triangle (Chalhoub et al., 2014; Yang et al., 2016a). [...] }}</ref>


The theory is summarized by a triangular diagram that shows the three ancestral genomes, denoted by AA, BB, and CC, at the corners of the triangle, and the three derived ones, denoted by AABB, AACC, and BBCC, along its sides.
The theory is summarized by a triangular diagram that shows the three ancestral genomes, denoted by AA, BB, and CC, at the corners of the triangle, and the three derived ones, denoted by AABB, AACC, and BBCC, along its sides.
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The theory was first published in 1935 by [[Woo Jang-choon]],<ref name=woo1935>{{cite journal |author=Nagaharu U |year=1935 |title=Genome analysis in Brassica with special reference to the experimental formation of B. napus and peculiar mode of fertilization |journal=Japan. J. Bot |volume=7 |pages=389–452|author-link=Woo Jang-choon }}</ref> a [[Korean people|Korean]]-[[Japanese people|Japanese]] [[botanist]] (writing under the Japanized name "Nagaharu U").<ref>{{cite web |url=http://junior.sciencetimes.co.kr/data/article/7000/0000006890.jsp |title=인터넷 과학신문 사이언스 타임즈 |language=ko |archive-url=https://web.archive.org/web/20070927014758/http://junior.sciencetimes.co.kr/data/article/7000/0000006890.jsp |archive-date=2007-09-27 |url-status=dead}}</ref> Woo made synthetic hybrids between the [[diploid]] and [[tetraploid]] species and examined how the chromosomes paired in the resulting triploids.
The theory was first published in 1935 by [[Woo Jang-choon]],<ref name=woo1935>{{cite journal |author=Nagaharu U |year=1935 |title=Genome analysis in Brassica with special reference to the experimental formation of B. napus and peculiar mode of fertilization |journal=Japan. J. Bot |volume=7 |pages=389–452|author-link=Woo Jang-choon }}</ref> a [[Korean people|Korean]]-[[Japanese people|Japanese]] [[botanist]] (writing under the Japanized name "Nagaharu U").<ref>{{cite web |url=http://junior.sciencetimes.co.kr/data/article/7000/0000006890.jsp |title=인터넷 과학신문 사이언스 타임즈 |language=ko |archive-url=https://web.archive.org/web/20070927014758/http://junior.sciencetimes.co.kr/data/article/7000/0000006890.jsp |archive-date=2007-09-27 |url-status=dead}}</ref> Woo made synthetic hybrids between the [[diploid]] and [[tetraploid]] species and examined how the chromosomes paired in the resulting triploids.


==Overview==
==U's theory==
The six species are
The six species are


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The code in the "Chr.Count" column specifies the total number of chromosomes in each somatic cell, and how it relates to the number "n" of [[chromosome]]s in each full genome set (which is also the number found in the pollen or [[ovule]]), and the number "x" of chromosomes in each component genome. For example, each somatic cell of the tetraploid species ''Brassica napus'', with letter tags AACC and count "2n=4x=38", contains two copies of the A genome, each with 10 chromosomes, and two copies of the C genome, each with 9 chromosomes, which is 38 chromosomes in total. That is two full genome sets (one A and one C), hence "2n=38" which means "n=19" (the number of chromosomes in each [[gamete]]). It is also four component genomes (two A and two C), hence "4x=38".{{Cn|date=January 2021}}
The code in the "Chr.Count" column specifies the total number of chromosomes in each somatic cell, and how it relates to the number "n" of [[chromosome]]s in each full genome set (which is also the number found in the pollen or [[ovule]]), and the number "x" of chromosomes in each component genome. For example, each somatic cell of the tetraploid species ''Brassica napus'', with letter tags AACC and count "2n=4x=38", contains two copies of the A genome, each with 10 chromosomes, and two copies of the C genome, each with 9 chromosomes, which is 38 chromosomes in total. That is two full genome sets (one A and one C), hence "2n=38" which means "n=19" (the number of chromosomes in each [[gamete]]). It is also four component genomes (two A and two C), hence "4x=38".<ref name=pmid32595682/>


The three diploid species exist in nature, but can easily interbreed because they are closely related. This [[interspecific breeding]] allowed for the creation of three new species of tetraploid ''Brassica''. These are said to be [[allotetraploid]] (containing four genomes from two or more different species); more specifically, [[amphidiploid]] (with two genomes each from two diploid species).{{Cn|date=January 2021}}
The three diploid species exist in nature, but can easily interbreed because they are closely related. This [[interspecific breeding]] allowed for the creation of three new species of tetraploid ''Brassica''.<ref name=woo1935/> (Critics, however, consider the geological separation too large.) These are said to be [[allotetraploid]] (containing four genomes from two or more different species); more specifically, [[amphidiploid]] (with two genomes each from two diploid species).<ref name=pmid32595682/>

== Further relationships ==
The framework proposed by U, although backed by modern studies, leaves open question about the time and place of hybridization and which species is the maternal or paternal parent. ''B. napus'' (AACC) is dated to have originated about 8000<ref name=pmid25146293/> or 38000&ndash;51000<ref name=pmid27595476>{{cite journal |last1=Yang |first1=J |last2=Liu |first2=D |last3=Wang |first3=X |last4=Ji |first4=C |last5=Cheng |first5=F |last6=Liu |first6=B |last7=Hu |first7=Z |last8=Chen |first8=S |last9=Pental |first9=D |last10=Ju |first10=Y |last11=Yao |first11=P |last12=Li |first12=X |last13=Xie |first13=K |last14=Zhang |first14=J |last15=Wang |first15=J |last16=Liu |first16=F |last17=Ma |first17=W |last18=Shopan |first18=J |last19=Zheng |first19=H |last20=Mackenzie |first20=SA |last21=Zhang |first21=M |title=The genome sequence of allopolyploid Brassica juncea and analysis of differential homoeolog gene expression influencing selection. |journal=Nature genetics |date=October 2016 |volume=48 |issue=10 |pages=1225-32 |doi=10.1038/ng.3657 |pmid=27595476 |doi-access=free}}</ref> years ago. The homologous part of its constituent chromosomes has [[Chromosomal crossover|crossed over]] in many cultivars.<ref name=pmid25146293>{{cite journal |last1=Chalhoub |first1=B |last2=Denoeud |first2=F |last3=Liu |first3=S |last4=Parkin |first4=IA |last5=Tang |first5=H |last6=Wang |first6=X |last7=Chiquet |first7=J |last8=Belcram |first8=H |last9=Tong |first9=C |last10=Samans |first10=B |last11=Corréa |first11=M |last12=Da Silva |first12=C |last13=Just |first13=J |last14=Falentin |first14=C |last15=Koh |first15=CS |last16=Le Clainche |first16=I |last17=Bernard |first17=M |last18=Bento |first18=P |last19=Noel |first19=B |last20=Labadie |first20=K |last21=Alberti |first21=A |last22=Charles |first22=M |last23=Arnaud |first23=D |last24=Guo |first24=H |last25=Daviaud |first25=C |last26=Alamery |first26=S |last27=Jabbari |first27=K |last28=Zhao |first28=M |last29=Edger |first29=PP |last30=Chelaifa |first30=H |last31=Tack |first31=D |last32=Lassalle |first32=G |last33=Mestiri |first33=I |last34=Schnel |first34=N |last35=Le Paslier |first35=MC |last36=Fan |first36=G |last37=Renault |first37=V |last38=Bayer |first38=PE |last39=Golicz |first39=AA |last40=Manoli |first40=S |last41=Lee |first41=TH |last42=Thi |first42=VH |last43=Chalabi |first43=S |last44=Hu |first44=Q |last45=Fan |first45=C |last46=Tollenaere |first46=R |last47=Lu |first47=Y |last48=Battail |first48=C |last49=Shen |first49=J |last50=Sidebottom |first50=CH |last51=Wang |first51=X |last52=Canaguier |first52=A |last53=Chauveau |first53=A |last54=Bérard |first54=A |last55=Deniot |first55=G |last56=Guan |first56=M |last57=Liu |first57=Z |last58=Sun |first58=F |last59=Lim |first59=YP |last60=Lyons |first60=E |last61=Town |first61=CD |last62=Bancroft |first62=I |last63=Wang |first63=X |last64=Meng |first64=J |last65=Ma |first65=J |last66=Pires |first66=JC |last67=King |first67=GJ |last68=Brunel |first68=D |last69=Delourme |first69=R |last70=Renard |first70=M |last71=Aury |first71=JM |last72=Adams |first72=KL |last73=Batley |first73=J |last74=Snowdon |first74=RJ |last75=Tost |first75=J |last76=Edwards |first76=D |last77=Zhou |first77=Y |last78=Hua |first78=W |last79=Sharpe |first79=AG |last80=Paterson |first80=AH |last81=Guan |first81=C |last82=Wincker |first82=P |title=Plant genetics. Early allopolyploid evolution in the post-Neolithic Brassica napus oilseed genome. |journal=Science (New York, N.Y.) |date=22 August 2014 |volume=345 |issue=6199 |pages=950-3 |doi=10.1126/science.1253435 |pmid=25146293 |url=https://www.researchgate.net/publication/267755510}}</ref> ''B. juncea'' (AABB) is estimated to have originated 39,000&ndash;55,000 years ago.<ref name=pmid27595476/> As of 2020, research on organellar genomes shows that ''B. nigra'' (BB) is likely the "mother" of ''B. carinata'' (BBCC) and that ''B. rapa'' (AA) likely mothered ''B. juncea''. The situation with ''B. napus'' is more complex.<ref name=pmid32595682/>


Data from molecular studies indicate the three diploid species are themselves [[paleopolyploid|paleohexaploid]]s.<ref>{{cite journal
Data from molecular studies indicate the three diploid species are themselves [[paleopolyploid|paleohexaploid]]s.<ref>{{cite journal

Revision as of 13:27, 27 November 2021

Triangle of U
The "triangle of U" diagram, showing the genetic relationships among six species of the genus Brassica. Chromosomes from each of the genomes A, B and C are represented by different colours.

The triangle of U (/uː/ OO) is a theory about the evolution and relationships among members of the plant genus Brassica. The theory states that the genomes of three ancestral diploid species of Brassica combined to create three common tetraploid vegetables and oilseed crop species.[1] It has since been confirmed by studies of DNA and proteins.[2]

The theory is summarized by a triangular diagram that shows the three ancestral genomes, denoted by AA, BB, and CC, at the corners of the triangle, and the three derived ones, denoted by AABB, AACC, and BBCC, along its sides.

The theory was first published in 1935 by Woo Jang-choon,[3] a Korean-Japanese botanist (writing under the Japanized name "Nagaharu U").[4] Woo made synthetic hybrids between the diploid and tetraploid species and examined how the chromosomes paired in the resulting triploids.

U's theory

The six species are

Genomes Chr.Count Species Description
Diploid
AA 2n=2x=20 Brassica rapa (syn. Brassica campestris) turnip, Chinese cabbage
BB 2n=2x=16 Brassica nigra black mustard
CC 2n=2x=18 Brassica oleracea cabbage, kale, broccoli, Brussels sprouts, cauliflower, kohlrabi
Tetraploid
AABB 2n=4x=36 Brassica juncea Indian mustard
AACC 2n=4x=38 Brassica napus rapeseed, rutabaga
BBCC 2n=4x=34 Brassica carinata Ethiopian mustard

The code in the "Chr.Count" column specifies the total number of chromosomes in each somatic cell, and how it relates to the number "n" of chromosomes in each full genome set (which is also the number found in the pollen or ovule), and the number "x" of chromosomes in each component genome. For example, each somatic cell of the tetraploid species Brassica napus, with letter tags AACC and count "2n=4x=38", contains two copies of the A genome, each with 10 chromosomes, and two copies of the C genome, each with 9 chromosomes, which is 38 chromosomes in total. That is two full genome sets (one A and one C), hence "2n=38" which means "n=19" (the number of chromosomes in each gamete). It is also four component genomes (two A and two C), hence "4x=38".[2]

The three diploid species exist in nature, but can easily interbreed because they are closely related. This interspecific breeding allowed for the creation of three new species of tetraploid Brassica.[3] (Critics, however, consider the geological separation too large.) These are said to be allotetraploid (containing four genomes from two or more different species); more specifically, amphidiploid (with two genomes each from two diploid species).[2]

Further relationships

The framework proposed by U, although backed by modern studies, leaves open question about the time and place of hybridization and which species is the maternal or paternal parent. B. napus (AACC) is dated to have originated about 8000[5] or 38000–51000[6] years ago. The homologous part of its constituent chromosomes has crossed over in many cultivars.[5] B. juncea (AABB) is estimated to have originated 39,000–55,000 years ago.[6] As of 2020, research on organellar genomes shows that B. nigra (BB) is likely the "mother" of B. carinata (BBCC) and that B. rapa (AA) likely mothered B. juncea. The situation with B. napus is more complex.[2]

Data from molecular studies indicate the three diploid species are themselves paleohexaploids.[7][8]

Allohexaploid species

In 2011 and 2018, a novel allohexaploid (AABBCC) which is located at the "center" of the triangle of U was created by different means,[9][10][11] for example by crossing B. rapa (AA) with B. carinata (BBCC), or B. nigra (BB) with B. napus (AACC), or B. oleracea (CC) with B. juncea (AABB), followed by chromosome duplication of the triploid (ABC) offspring to generate doubled haploid (AABBCC) offspring.[12][13] In addition, a stable allohexaploid (AABBSS) intergeneric hybrid between Indian mustard (B. juncea, AABB) and white mustard (Sinapsis alba, SS) was reported in 2020.[14]

See also

References

  1. ^ Jules, Janick (2009). Plant Breeding Reviews. Vol. 31. Wiley. p. 56. ISBN 978-0-470-38762-7.
  2. ^ a b c d Xue, JY; Wang, Y; Chen, M; Dong, S; Shao, ZQ; Liu, Y (2020). "Maternal Inheritance of U's Triangle and Evolutionary Process of Brassica Mitochondrial Genomes". Frontiers in plant science. 11: 805. doi:10.3389/fpls.2020.00805. PMID 32595682. Comparative genomic analyses can assign the subgenomes of the allotetraploids, B. juncea and B. napus, with their diploid parental taxa, and the results were in agreement with U's triangle (Chalhoub et al., 2014; Yang et al., 2016a). [...]
  3. ^ a b Nagaharu U (1935). "Genome analysis in Brassica with special reference to the experimental formation of B. napus and peculiar mode of fertilization". Japan. J. Bot. 7: 389–452.
  4. ^ "인터넷 과학신문 사이언스 타임즈" (in Korean). Archived from the original on 2007-09-27.
  5. ^ a b Chalhoub, B; Denoeud, F; Liu, S; Parkin, IA; Tang, H; Wang, X; Chiquet, J; Belcram, H; Tong, C; Samans, B; Corréa, M; Da Silva, C; Just, J; Falentin, C; Koh, CS; Le Clainche, I; Bernard, M; Bento, P; Noel, B; Labadie, K; Alberti, A; Charles, M; Arnaud, D; Guo, H; Daviaud, C; Alamery, S; Jabbari, K; Zhao, M; Edger, PP; Chelaifa, H; Tack, D; Lassalle, G; Mestiri, I; Schnel, N; Le Paslier, MC; Fan, G; Renault, V; Bayer, PE; Golicz, AA; Manoli, S; Lee, TH; Thi, VH; Chalabi, S; Hu, Q; Fan, C; Tollenaere, R; Lu, Y; Battail, C; Shen, J; Sidebottom, CH; Wang, X; Canaguier, A; Chauveau, A; Bérard, A; Deniot, G; Guan, M; Liu, Z; Sun, F; Lim, YP; Lyons, E; Town, CD; Bancroft, I; Wang, X; Meng, J; Ma, J; Pires, JC; King, GJ; Brunel, D; Delourme, R; Renard, M; Aury, JM; Adams, KL; Batley, J; Snowdon, RJ; Tost, J; Edwards, D; Zhou, Y; Hua, W; Sharpe, AG; Paterson, AH; Guan, C; Wincker, P (22 August 2014). "Plant genetics. Early allopolyploid evolution in the post-Neolithic Brassica napus oilseed genome". Science (New York, N.Y.). 345 (6199): 950–3. doi:10.1126/science.1253435. PMID 25146293.
  6. ^ a b Yang, J; Liu, D; Wang, X; Ji, C; Cheng, F; Liu, B; Hu, Z; Chen, S; Pental, D; Ju, Y; Yao, P; Li, X; Xie, K; Zhang, J; Wang, J; Liu, F; Ma, W; Shopan, J; Zheng, H; Mackenzie, SA; Zhang, M (October 2016). "The genome sequence of allopolyploid Brassica juncea and analysis of differential homoeolog gene expression influencing selection". Nature genetics. 48 (10): 1225–32. doi:10.1038/ng.3657. PMID 27595476.
  7. ^ Martin A. Lysak; Kwok Cheung; Michaela Kitschke & Petr Bu (October 2007). "Ancestral Chromosomal Blocks Are Triplicated in Brassiceae Species with Varying Chromosome Number and Genome Size" (PDF). Plant Physiology. 145 (2): 402–10. doi:10.1104/pp.107.104380. PMC 2048728. PMID 17720758. Retrieved 2010-08-22.
  8. ^ Murat, Florent; Louis, Alexandra; Maumus, Florian; Armero, Alix; Cooke, Richard; Quesneville, Hadi; Crollius, Hugues Roest; Salse, Jerome (December 2015). "Understanding Brassicaceae evolution through ancestral genome reconstruction". Genome Biology. 16 (1): 262. doi:10.1186/s13059-015-0814-y.
  9. ^ Chen, Sheng; Nelson, Matthew N.; Chèvre, Anne-Marie; Jenczewski, Eric; Li, Zaiyun; Mason, Annaliese S.; Meng, Jinling; Plummer, Julie A.; Pradhan, Aneeta; Siddique, Kadambot H. M.; Snowdon, Rod J.; Yan, Guijun; Zhou, Weijun; Cowling, Wallace A. (2011-11-01). "Trigenomic Bridges for Brassica Improvement". Critical Reviews in Plant Sciences. 30 (6): 524–547. doi:10.1080/07352689.2011.615700. ISSN 0735-2689. S2CID 84504896.
  10. ^ Yang, Su; Chen, Sheng; Zhang, Kangni; Li, Lan; Yin, Yuling; Gill, Rafaqat A.; Yan, Guijun; Meng, Jinling; Cowling, Wallace A.; Zhou, Weijun (2018-08-28). "A High-Density Genetic Map of an Allohexaploid Brassica Doubled Haploid Population Reveals Quantitative Trait Loci for Pollen Viability and Fertility". Frontiers in Plant Science. 9: 1161. doi:10.3389/fpls.2018.01161. ISSN 1664-462X. PMC 6123574. PMID 30210508.
  11. ^ Gaebelein, Roman; Mason, Annaliese S. (2018-09-03). "Allohexaploids in the Genus Brassica". Critical Reviews in Plant Sciences. 37 (5): 422–437. doi:10.1080/07352689.2018.1517143. ISSN 0735-2689. S2CID 91439428.
  12. ^ "Correction to Lancet Infect Dis 2021; published online June 23". Lancet Infect Dis. 21 (8): e208. 2021. doi:10.1016/S1473-3099(21)00397-2. PMC 8318405. PMID 34237259.
  13. ^ Gaebelein, Roman; Mason, Annaliese S. (2018-09-03). "Allohexaploids in the Genus Brassica". Critical Reviews in Plant Sciences. 37 (5): 422–437. doi:10.1080/07352689.2018.1517143. ISSN 0735-2689.
  14. ^ Kumari P, Singh KP, Kumar S, Yadava DK (2020). "Development of a Yellow-Seeded Stable Allohexaploid Brassica Through Inter-Generic Somatic Hybridization With a High Degree of Fertility and Resistance to Sclerotinia sclerotiorum". Front Plant Sci. 11: 575591. doi:10.3389/fpls.2020.575591. PMC 7732669. PMID 33329636.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link)
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