Un Carbonic Anhydrase And The Molecular Evolution Of C4 Photosynthesispce 2364

Carbonic anhydrase and the molecular evolution of
C4 photosynthesispce_2364

ABSTRACT.
C4 photosynthesis, a biochemical CO2-concentrating mechanism
(CCM), evolved more than 60 times within the
angiosperms from C3 ancestors. The genus Flaveria, which
contains species demonstrating C3, C3–C4, C4-like or C4 photosynthesis,
is a model for examining the molecular evolution
of the C4 pathway.Work with carbonic anhydrase (CA),
and C3 and C4 Flaveria congeners has added significantly to
the understanding of this process. The C4 form of CA3, a
b-CA, which catalyses the first reaction in the C4 pathway by
hydrating atmospheric CO2 to bicarbonate in the cytosol of
mesophyll cells (mcs), evolved from a chloroplasticC3 ancestor.
The molecular modifications to the ancestral CA3 geneincluded the loss of the sequence encoding the chloroplast
transit peptide, and mutations in regulatory regions that
resulted in high levels of expression in the C4 mesophyll.
Analyses of the CA3 proteins and regulatory elements from
Flaveria photosynthetic intermediates indicated C4 biochemistry
very likely evolved in a specific, stepwise manner
in this genus. The details of the mechanismsinvolved in the
molecular evolution of other C4 plant b-CAs are unknown;
however,comparative genetics indicate gene duplication and
neofunctionalization played significant roles as they did in
Flaveria.

RESUMEN. Fotosíntesis C4, un mecanismo bioquímico de concentración de CO2 (CCM), evolucionó más de 60 veces dentro de las angiospermas de antepasados de C3. El género Flaveria, que contieneespecies demostrando C3, C3–C4, C4-como o fotosíntesis C4, es un modelo para examinar la evolución molecular de la vía de C4. Trabajar con la anhidrasa carbónica (CA), y congéneres C3 y C4 Flaveria ha añadido considerablemente a la comprensión de este proceso. La forma de C4 de fue, una b-CA, que cataliza la primera reacción en la vía de C4 por hidratante CO2 atmosférico a bicarbonato en elcitoplasma de las células mesophyll (mcs), evolucionaron de un antepasado de chloroplasticC3. Las modificaciones moleculares del gen fue ancestral incluyen la pérdida de la secuencia de codificación el péptido de tránsito cloroplasto y mutaciones en regiones reguladoras que dio lugar a altos niveles de expresión en el mesophyll C4. Análisis de proteínas fue los elementos reglamentarios de Flaveriafotosintéticos intermedios indican C4 bioquímica muy probablemente evolucionado de manera específica, paso a paso en este género. Se desconocen los detalles de los mecanismos que intervienen en la evolución molecular de otras plantas C4 b-CAs; Sin embargo, la genética comparativa indica duplicación génica y neofunctionalization jugado un papel importante como hicieron en Flaveria.

INTRODUCTION
TheC4 photosynthetic pathway is one of the most significant
complex adaptive traits ever acquired by angiosperms. The
evolution of C4 plants from their C3 ancestors at least 30
million years ago (Edwards et al. 2010), followed by their
expansion in the late Miocene, led to large-scale and lasting
changes in climate (Cowling, Jones & Cox 2007) and in
ecosystems by displacing C3 plants,modifying fire frequency
and influencing the distribution and evolution of C4 herbivores,
including humans (Ehleringer, Cerling & Helliker
1997; Cerling, Ehleringer & Harris 1998; van der Merwe &
Tschauner 1999; Keeley & Rundel 2005; Beerling &
Osborne 2006). Although only 3% of all vascular plant species use a C4 pathway (Sage 2004), these plants are
responsible for nearly25% of global primary productivity
(Lloyd & Farquhar 1994; Still et al. 2003), and are important
and successful taxa in tropical, subtropical and warm temperate
ecosystems, as well as in arid and saline habitats
(Sage,Wedin & Li 1999; Still et al. 2003). C4 grasses such as
Zea mays (maize), Sorghum bicolor (sorghum), Saccharum
spp. (sugar cane) and millets are important food and...