Box 1 (continued)
With land colonization, early (nonvascular) plants, such as bryophytes
(e.g., hornworts and mosses) where exposed to desiccation, the lack of structural support, and damaging UV-B radiation. The phenylpropanoid metabolism was crucial for plant vascularization and the occurrence of tracheophytes
in terrestrial ecosystems. Lignin, a phenolic polymer derived from
phenylpropanoid metabolism, synthetized from hydroxycinnamyl alcohols,
provides structural rigidity and regulates the hydration of the hydrophilic
molecules in the cell wall to bear the negative pressure generated during
transpiration. In addition, as most of phenolic acids derived from the aromatic
amino acids of algae and other photosynthetic eukaryotes, lignin function as
absorption agent of UV light [182]. Given these functional properties of lignin,
its accumulation in cell walls (i.e., lignification) has been considered a key
biosynthetic process for the success of land plants.
2.1
Secondary Metabolites and the Origin of Plant-Insect
Interaction
Since the emergence of first embryophyte land plants in mid Ordovician ~470 Mya,
to late Devonian and early Carboniferous ~360 Mya, many of the features recognized in land plants today were present, including roots, leaves, and early seeds. The
evolutionary innovation from the Carboniferous that still continues today is not only
restricted to photosynthetic eukaryotes. Fossil records suggest that ca. 100 Mya after
the emergence of vascular plants, evolution of arthropods took place during mid
Carboniferous (~300 Mya) [138, 150]. In late Paleozoic and early Mesozoic 250
Mya, important groups of phytophagous insects such as Coleoptera and Lepidoptera
appeared. Fossil records of damaged leaves, coprolite dispersion, specialized mouthparts and intestinal contents of orthopterans evince the origins of an antagonistic
interaction between plants and first phytophagous arthropods [84, 106, 107]. Interaction of plants and arthropods (especially insects) diversified extensively with the
emergence of flowering plants about 160 Mya and became widespread by 120 Mya
during the lower Cretaceous. Paleochemical analyses of ancient angiosperms from
late Mesozoic and early Cenozoic demonstrate an impressive increase in biochemical diversity, which include lignin derivatives, terpenoids, tannins, and flavonoids,
among others [37]. Most of these secondary metabolites derived from phenolic
metabolism are known from their toxic and deterrent effect on plant consumers (e.
g., flavonoids prevent pathogen invasion and affect the activity of digestive enzymes
of animals, [171, 178]). These findings suggest that although metabolites’ evolutionary origin may be associated with selective factors other than phytophagy (see
Box 1), their diversification might be related to the coexistence of angiosperms and
first arthropods. This whole paleontological and biochemical evidence has contribute to the notion that the diversification patterns of plants and arthropods instead of
only coincide in time rather reflects the reciprocal evolutionary influence of plants
and phytophagous insects, that arose from their interaction.
50
E. Kariñho-Betancourt
With land colonization, early (nonvascular) plants, such as bryophytes
(e.g., hornworts and mosses) where exposed to desiccation, the lack of structural support, and damaging UV-B radiation. The phenylpropanoid metabolism was crucial for plant vascularization and the occurrence of tracheophytes
in terrestrial ecosystems. Lignin, a phenolic polymer derived from
phenylpropanoid metabolism, synthetized from hydroxycinnamyl alcohols,
provides structural rigidity and regulates the hydration of the hydrophilic
molecules in the cell wall to bear the negative pressure generated during
transpiration. In addition, as most of phenolic acids derived from the aromatic
amino acids of algae and other photosynthetic eukaryotes, lignin function as
absorption agent of UV light [182]. Given these functional properties of lignin,
its accumulation in cell walls (i.e., lignification) has been considered a key
biosynthetic process for the success of land plants.
2.1
Secondary Metabolites and the Origin of Plant-Insect
Interaction
Since the emergence of first embryophyte land plants in mid Ordovician ~470 Mya,
to late Devonian and early Carboniferous ~360 Mya, many of the features recognized in land plants today were present, including roots, leaves, and early seeds. The
evolutionary innovation from the Carboniferous that still continues today is not only
restricted to photosynthetic eukaryotes. Fossil records suggest that ca. 100 Mya after
the emergence of vascular plants, evolution of arthropods took place during mid
Carboniferous (~300 Mya) [138, 150]. In late Paleozoic and early Mesozoic 250
Mya, important groups of phytophagous insects such as Coleoptera and Lepidoptera
appeared. Fossil records of damaged leaves, coprolite dispersion, specialized mouthparts and intestinal contents of orthopterans evince the origins of an antagonistic
interaction between plants and first phytophagous arthropods [84, 106, 107]. Interaction of plants and arthropods (especially insects) diversified extensively with the
emergence of flowering plants about 160 Mya and became widespread by 120 Mya
during the lower Cretaceous. Paleochemical analyses of ancient angiosperms from
late Mesozoic and early Cenozoic demonstrate an impressive increase in biochemical diversity, which include lignin derivatives, terpenoids, tannins, and flavonoids,
among others [37]. Most of these secondary metabolites derived from phenolic
metabolism are known from their toxic and deterrent effect on plant consumers (e.
g., flavonoids prevent pathogen invasion and affect the activity of digestive enzymes
of animals, [171, 178]). These findings suggest that although metabolites’ evolutionary origin may be associated with selective factors other than phytophagy (see
Box 1), their diversification might be related to the coexistence of angiosperms and
first arthropods. This whole paleontological and biochemical evidence has contribute to the notion that the diversification patterns of plants and arthropods instead of
only coincide in time rather reflects the reciprocal evolutionary influence of plants
and phytophagous insects, that arose from their interaction.
50
E. Kariñho-Betancourt