Genetic and isotope ratio mass spectrometric evidence for the occurrence of starch degradation and cycling in illuminated Arabidopsis leaves
Fecha
2017Autor
Versión
Acceso abierto / Sarbide irekia
Tipo
Artículo / Artikulua
Versión
Versión publicada / Argitaratu den bertsioa
Impacto
|
10.1371/journal.pone.0171245
Resumen
Although there is a great wealth of data supporting the occurrence of simultaneous synthesis
and breakdown of storage carbohydrate in many organisms, previous 13CO2 pulse-chase
based studies indicated that starch degradation does not operate in illuminated Arabidopsis
leaves. Here we show that leaves of gwd, sex4, bam4, bam1/bam3 and amy3/isa3/lda starch
breakdown mutants accumulate higher le ...
[++]
Although there is a great wealth of data supporting the occurrence of simultaneous synthesis
and breakdown of storage carbohydrate in many organisms, previous 13CO2 pulse-chase
based studies indicated that starch degradation does not operate in illuminated Arabidopsis
leaves. Here we show that leaves of gwd, sex4, bam4, bam1/bam3 and amy3/isa3/lda starch
breakdown mutants accumulate higher levels of starch than wild type (WT) leaves when cultured
under continuous light (CL) conditions. We also show that leaves of CL grown dpe1
plants impaired in the plastidic disproportionating enzyme accumulate higher levels of maltotriose
than WT leaves, the overall data providing evidence for the occurrence of extensive
starch degradation in illuminated leaves. Moreover, we show that leaves of CL grown mex1/
pglct plants impaired in the chloroplastic maltose and glucose transporters display a severe
dwarf phenotype and accumulate high levels of maltose, strongly indicating that the MEX1
and pGlcT transporters are involved in the export of starch breakdown products to the cytosol
to support growth during illumination. To investigate whether starch breakdown products can
be recycled back to starch during illumination through a mechanism involving ADP-glucose
pyrophosphorylase (AGP) we conducted kinetic analyses of the stable isotope carbon composition
(δ13C) in starch of leaves of 13CO2 pulsed-chased WT and AGP lacking aps1 plants.
Notably, the rate of increase of δ13C in starch of aps1 leaves during the pulse was exceedingly
higher than that of WT leaves. Furthermore, δ13C decline in starch of aps1 leaves during
the chase was much faster than that of WT leaves, which provides strong evidence for the
occurrence of AGP-mediated cycling of starch breakdown products in illuminated Arabidopsis
leaves. [--]
Materias
Arabidopsis leaves,
Starch
Editor
Public Library of Science
Publicado en
Plos One, 12(2): e0171245.
Departamento
Universidad Pública de Navarra/Nafarroako Unibertsitate Publikoa. IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
Versión del editor
Entidades Financiadoras
Comisión Interministerial de Ciencia y Tecnología and Fondo Europeo de Desarrollo Regional (Spain) Grant numbers: BIO2010-18239 and BIO2013-49125-C2-1-P.