Proteome Modification in Tomato Plants upon Long-Term Aluminum Treatment

This study aimed
to identify the aluminum (Al)-induced proteomes
in tomato (Solanum lycopersicum, “Micro-Tom”)
after long-term exposure to the stress factor. Plants were treated
in Magnavaca’s solution (pH 4.5) supplemented with 7.5 μM
Al3+ ion activity over a 4 month period beginning at the
emergence of flower buds and ending when the lower mature leaves started
to turn yellow. Proteomes were identified using a 8-plex isobaric
tags for relative and absolute quantification (iTRAQ) labeling strategy
followed by a two-dimensional (high- and low-pH) chromatographic separation
and final generation of tandem mass spectrometry (MS/MS) spectra of
tryptic peptides on an LTQ-Orbitrap Elite mass spectrometer. Principal
component analysis revealed that the Al-treatment had induced systemic
alterations in the proteomes from roots and leaves but not seed tissues.
The significantly changed root proteins were shown to have putative
functions in Al3+ ion uptake and transportation, root development,
and a multitude of other cellular processes. Changes in the leaf proteome
indicate that the light reaction centers of photosynthetic machinery
are the primary targets of Al-induced stress. Embryo and seed-coat
tissues derived from Al-treated plants were enriched with stress proteins.
The biological processes involving these Al-induced proteins concur
with the physiological and morphological changes, such as the disturbance
of mineral homeostasis (higher contents of Al, P, and Fe and reduced
contents of S, Zn, and Mn in Al-treated compared to nontreated plants)
in roots and smaller sizes of roots and the whole plants. More importantly,
the identified significant proteins might represent a molecular mechanism
for plants to develop toward establishing the Al tolerance and adaptation
mechanism over a long period of stress treatment.