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Genetic control of inflorescence architecture in legumes.

Benlloch R, Berbel A, Ali L, Gohari G, Millán T, Madueño F - Front Plant Sci (2015)

Bottom Line: The architecture of the inflorescence, the shoot system that bears the flowers, is a main component of the huge diversity of forms found in flowering plants.In contrast, legumes represent a more complex inflorescence type, the compound inflorescence, where flowers are not directly borne in the main inflorescence axis but, instead, they are formed by secondary or higher order inflorescence meristems.Studies in model legumes such as pea (Pisum sativum) or Medicago truncatula have led to a rather good knowledge of the genetic control of the development of the legume compound inflorescence.

View Article: PubMed Central - PubMed

Affiliation: Molecular Genetics Department, Center for Research in Agricultural Genomics, Consortium CSIC-IRTA-UAB-UB, Parc de Recerca Universitat Autònoma de Barcelona Barcelona, Spain.

ABSTRACT
The architecture of the inflorescence, the shoot system that bears the flowers, is a main component of the huge diversity of forms found in flowering plants. Inflorescence architecture has also a strong impact on the production of fruits and seeds, and on crop management, two highly relevant agronomical traits. Elucidating the genetic networks that control inflorescence development, and how they vary between different species, is essential to understanding the evolution of plant form and to being able to breed key architectural traits in crop species. Inflorescence architecture depends on the identity and activity of the meristems in the inflorescence apex, which determines when flowers are formed, how many are produced and their relative position in the inflorescence axis. Arabidopsis thaliana, where the genetic control of inflorescence development is best known, has a simple inflorescence, where the primary inflorescence meristem directly produces the flowers, which are thus borne in the main inflorescence axis. In contrast, legumes represent a more complex inflorescence type, the compound inflorescence, where flowers are not directly borne in the main inflorescence axis but, instead, they are formed by secondary or higher order inflorescence meristems. Studies in model legumes such as pea (Pisum sativum) or Medicago truncatula have led to a rather good knowledge of the genetic control of the development of the legume compound inflorescence. In addition, the increasing availability of genetic and genomic tools for legumes is allowing to rapidly extending this knowledge to other grain legume crops. This review aims to describe the current knowledge of the genetic network controlling inflorescence development in legumes. It also discusses how the combination of this knowledge with the use of emerging genomic tools and resources may allow rapid advances in the breeding of grain legume crops.

No MeSH data available.


Meristem identity genes in pea. (A) Picture and diagram of a pea WT plant. The main primary inflorescence (I1) shows indeterminate growth (arrowhead). Upper nodes of the plant contain secondary inflorescences (I2) which produce 1–2 flowers (F, open circles) and terminate into a stub (triangles). The inset shows a close up of a secondary inflorescence with two flowers (pods) and the stub (arrowhead). (B) Diagrams of meristem identity of the pim, det, and veg1 mutants. In the pim mutant, flowers are replaced by proliferating I2s with abnormal flowers (closed circles). In the det mutant, the primary inflorescence is replaced by a terminal secondary inflorescence. In the veg1 mutant, the I2s are replaced by vegetative branches with I1 identity. (C) Model for specification of meristem identity in the compound pea inflorescence. In the pea inflorescence apex, DET expression in the primary inflorescence meristem (I2), VEG1 in the secondary inflorescence meristem (I2) and PIM in the floral meristem (F) are required for these meristems to acquire their identity. Expression of these genes in their correct domains is maintained by a network of mutual repressive interactions.
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Figure 3: Meristem identity genes in pea. (A) Picture and diagram of a pea WT plant. The main primary inflorescence (I1) shows indeterminate growth (arrowhead). Upper nodes of the plant contain secondary inflorescences (I2) which produce 1–2 flowers (F, open circles) and terminate into a stub (triangles). The inset shows a close up of a secondary inflorescence with two flowers (pods) and the stub (arrowhead). (B) Diagrams of meristem identity of the pim, det, and veg1 mutants. In the pim mutant, flowers are replaced by proliferating I2s with abnormal flowers (closed circles). In the det mutant, the primary inflorescence is replaced by a terminal secondary inflorescence. In the veg1 mutant, the I2s are replaced by vegetative branches with I1 identity. (C) Model for specification of meristem identity in the compound pea inflorescence. In the pea inflorescence apex, DET expression in the primary inflorescence meristem (I2), VEG1 in the secondary inflorescence meristem (I2) and PIM in the floral meristem (F) are required for these meristems to acquire their identity. Expression of these genes in their correct domains is maintained by a network of mutual repressive interactions.

Mentions: As mentioned above, legumes are characterized by a compound indeterminate inflorescence (Weberling, 1989b; Benlloch et al., 2007; Prenner, 2013; Hofer and Noel Ellis, 2014). The ontogeny of the compound inflorescence has been described in detail in pea (Pisum sativum; Singer et al., 1999). Briefly, the SAM undergoes a transition from a vegetative meristem to a primary inflorescence (I1) meristem, with indeterminate growth. This I1 meristem, instead of producing floral meristems at its flanks, as in the case of Arabidopsis, produces secondary inflorescence meristems (I2), which in turn will generate floral meristems (F). In pea, the I2 usually produces 1-2 floral meristems before it ceases growing, forming a residual organ or stub (Figure 3). Therefore, the appearance of the I2 meristem supposes an additional level of complexity in the legume inflorescence, as compared to Arabidopsis, and different genes have been coopted to orchestrate the development of the compound inflorescence in legumes.


Genetic control of inflorescence architecture in legumes.

Benlloch R, Berbel A, Ali L, Gohari G, Millán T, Madueño F - Front Plant Sci (2015)

Meristem identity genes in pea. (A) Picture and diagram of a pea WT plant. The main primary inflorescence (I1) shows indeterminate growth (arrowhead). Upper nodes of the plant contain secondary inflorescences (I2) which produce 1–2 flowers (F, open circles) and terminate into a stub (triangles). The inset shows a close up of a secondary inflorescence with two flowers (pods) and the stub (arrowhead). (B) Diagrams of meristem identity of the pim, det, and veg1 mutants. In the pim mutant, flowers are replaced by proliferating I2s with abnormal flowers (closed circles). In the det mutant, the primary inflorescence is replaced by a terminal secondary inflorescence. In the veg1 mutant, the I2s are replaced by vegetative branches with I1 identity. (C) Model for specification of meristem identity in the compound pea inflorescence. In the pea inflorescence apex, DET expression in the primary inflorescence meristem (I2), VEG1 in the secondary inflorescence meristem (I2) and PIM in the floral meristem (F) are required for these meristems to acquire their identity. Expression of these genes in their correct domains is maintained by a network of mutual repressive interactions.
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Figure 3: Meristem identity genes in pea. (A) Picture and diagram of a pea WT plant. The main primary inflorescence (I1) shows indeterminate growth (arrowhead). Upper nodes of the plant contain secondary inflorescences (I2) which produce 1–2 flowers (F, open circles) and terminate into a stub (triangles). The inset shows a close up of a secondary inflorescence with two flowers (pods) and the stub (arrowhead). (B) Diagrams of meristem identity of the pim, det, and veg1 mutants. In the pim mutant, flowers are replaced by proliferating I2s with abnormal flowers (closed circles). In the det mutant, the primary inflorescence is replaced by a terminal secondary inflorescence. In the veg1 mutant, the I2s are replaced by vegetative branches with I1 identity. (C) Model for specification of meristem identity in the compound pea inflorescence. In the pea inflorescence apex, DET expression in the primary inflorescence meristem (I2), VEG1 in the secondary inflorescence meristem (I2) and PIM in the floral meristem (F) are required for these meristems to acquire their identity. Expression of these genes in their correct domains is maintained by a network of mutual repressive interactions.
Mentions: As mentioned above, legumes are characterized by a compound indeterminate inflorescence (Weberling, 1989b; Benlloch et al., 2007; Prenner, 2013; Hofer and Noel Ellis, 2014). The ontogeny of the compound inflorescence has been described in detail in pea (Pisum sativum; Singer et al., 1999). Briefly, the SAM undergoes a transition from a vegetative meristem to a primary inflorescence (I1) meristem, with indeterminate growth. This I1 meristem, instead of producing floral meristems at its flanks, as in the case of Arabidopsis, produces secondary inflorescence meristems (I2), which in turn will generate floral meristems (F). In pea, the I2 usually produces 1-2 floral meristems before it ceases growing, forming a residual organ or stub (Figure 3). Therefore, the appearance of the I2 meristem supposes an additional level of complexity in the legume inflorescence, as compared to Arabidopsis, and different genes have been coopted to orchestrate the development of the compound inflorescence in legumes.

Bottom Line: The architecture of the inflorescence, the shoot system that bears the flowers, is a main component of the huge diversity of forms found in flowering plants.In contrast, legumes represent a more complex inflorescence type, the compound inflorescence, where flowers are not directly borne in the main inflorescence axis but, instead, they are formed by secondary or higher order inflorescence meristems.Studies in model legumes such as pea (Pisum sativum) or Medicago truncatula have led to a rather good knowledge of the genetic control of the development of the legume compound inflorescence.

View Article: PubMed Central - PubMed

Affiliation: Molecular Genetics Department, Center for Research in Agricultural Genomics, Consortium CSIC-IRTA-UAB-UB, Parc de Recerca Universitat Autònoma de Barcelona Barcelona, Spain.

ABSTRACT
The architecture of the inflorescence, the shoot system that bears the flowers, is a main component of the huge diversity of forms found in flowering plants. Inflorescence architecture has also a strong impact on the production of fruits and seeds, and on crop management, two highly relevant agronomical traits. Elucidating the genetic networks that control inflorescence development, and how they vary between different species, is essential to understanding the evolution of plant form and to being able to breed key architectural traits in crop species. Inflorescence architecture depends on the identity and activity of the meristems in the inflorescence apex, which determines when flowers are formed, how many are produced and their relative position in the inflorescence axis. Arabidopsis thaliana, where the genetic control of inflorescence development is best known, has a simple inflorescence, where the primary inflorescence meristem directly produces the flowers, which are thus borne in the main inflorescence axis. In contrast, legumes represent a more complex inflorescence type, the compound inflorescence, where flowers are not directly borne in the main inflorescence axis but, instead, they are formed by secondary or higher order inflorescence meristems. Studies in model legumes such as pea (Pisum sativum) or Medicago truncatula have led to a rather good knowledge of the genetic control of the development of the legume compound inflorescence. In addition, the increasing availability of genetic and genomic tools for legumes is allowing to rapidly extending this knowledge to other grain legume crops. This review aims to describe the current knowledge of the genetic network controlling inflorescence development in legumes. It also discusses how the combination of this knowledge with the use of emerging genomic tools and resources may allow rapid advances in the breeding of grain legume crops.

No MeSH data available.