Abiotic Stress Responses in Plants: Unraveling the Complexity of Genes and Networks to Survive - Abiotic Stress: Plant Responses and Applications in Agriculture - page 73

compared to the proteome of the same plant under study conditions such as the exposure to
a heavy metal or water deficit, or in another example the comparison of protein expression
profiles between different varieties of wheat.
Proteomics is heavily dependent on two laboratory techniques, protein electrophoresis
(particularly two-dimensional electrophoresis and DIGE - Difference In Gel Electrophoresis)
and protein identification using mass spectrometry. For further information on these ap‐
proaches, kindly refer to the reviews by Minden [295] and Soares et al. [296] on respectively
DIGE and mass spectrometry based protein identification strategies. Proteomics, particularly
differential proteomics, has been widely applied to the study of the effects of several abiotic
stresses on plant organs and tissues. The subject has been the object of a recent and extensive
review [297]. For this reason, in this section we will provide examples on the use of proteomics
to study the effects of abiotic stress in plants.
Evers et al. [298] have used both transcriptomics and proteomics to study the effects of cold
and salt stresses on the leaf transcriptome and proteome of potato ( Solanum tuberosum ). Results
pointed out to a number differentially regulated genes and proteins at the level of both stresses.
Interestingly, salt exposure results displayed a strong down-regulation of genes implicated in
primary metabolism, detoxication apparatus and signal transduction, whereas upon cold
exposure, up and down-regulated genes were similar in number. On the contrary, proteome
analysis seems to point out to an increase in protein expression of almost every protein with
the exception of those with a role in photosynthesis. The results from this study highlight not
only the differences between transcriptome and proteome expression as a consequence of cold
and salt stresses but it particularly shows how the proteome analysis tends to be much more
thorough and complete than transcriptome analysis.
In another example, DIGE has been used to study the effects of high level of UV radiation on
the leaf proteome of artichoke, particularly targeting the levels of inducible antioxidants
present in this species [299]. Authors observed a total of 145 spots showing differential
expression and were able to identify 111 of them. Most of the proteins differentially modulated
were chloroplast located, involved in photosynthesis, sugar metabolisms, protein folding and
stress responsive, shedding a new understanding on the physiological and metabolic alterna‐
tions induced by UV radiation exposure.
The embryo proteome of six rice varieties subjected to water deficit stress has been com‐
pared in order to further understand the mechanisms leading to water-stress tolerance in
this crop [300]. A total of 28 proteins were identified involved in stress tolerance (LEA
proteins), nutrient reservoir activity, among other proteins implicated in diverse cellular
processes potentially related to the stress response (e.g., mitochondrial import translo‐
case) in this cereal. Authors were also able to identify several differences and the post-
translational level, particularly in the late embryogenesis abundant Rab21 that was more
strongly phosphorylated in the embryos of the sensitive varieties than in the embryos of
the tolerant ones. Similarly to the example by Evers previously mentioned, this study
clearly demonstrates the broadness and completeness of proteome studies, particularly at
the level of Post Translational Modifications (PTMs).