Plant Responses and Tolerance in Stress: A System Biology Perspective

This paper critically reviews the plant responses and tolerance in stress such as drought from a physiological and molecular perspective using system biology approach.

Running head: SYSTEM BIOLOGY
Name of the Student
Name of the University
Author Note

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Introduction:
The natural environment for plant encompasses a complex set of abiotic and biotic
stresses. The response of plants against these stresses are also a complex approach (Franzosa et
al., 2016). However, system biology explored the molecular part such as transcription, proteins,
and metabolism of an organism and subjected it in the functional network designed to gain the
understanding of the dynamics activities of that plants in a diverse environment (Naba et al.,
2016). The purpose of this paper is to critically review the plant responses and tolerance in stress
such drought from a physiological and molecular perspective. This paper will discuss the
different omics approach to stress tolerance in plants in the following paragraphs.
Discussion:
Plants are complex organisms where various complexity is present within multiple
organisms and interactions between nuclear, plastidial and mitochondrial genome are responsible
for the different stress response of plants. A typical plant cell had more than 30000 genes with
unknown protein which have 200 known post-translation modifications which are responsible for
diverse responses of plant against abiotic or biotic stress (Faghani et al. 2016). Since these stress
responses are not possible to identify with simple lab experiments, system biology offers an in-
depth understanding of these complex responses from the perspective of transcriptomics,
proteomics and genomics. Taking an insight into the physiology of drought response in the
plant, when the plant is subjected to water shortage, they may experience short term water
deficit and adapt accordingly. The plant is more susceptible to drought during the reproductive
period and adapts to the stress by minimizing water loss, maximizing water intake. In responses
to drought condition, there is an alteration of the gene expression observed which are induced by

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transcription factors. Iovieno et al. (2016) conducted a transcriptomics study on tomato where
researchers analyzed physiological responses with the help of stomatal conductance, co2
assimilation, chlorophyll fluorescence. Abscise acid, proline content and multiple metabolic
assays to generate transcriptomes at multipoint during stress and recovery cycle. The result
suggested that the minimization of water intake inhibit the photosynthesis process which affected
the plant growth. The low Fv/Fm ratio at Dr1 indicated the photoinactivation had observed in
psi. The researchers found that two isoforms of subunit A of nuclear factors NF-YA7 and NF-
YA10 were also induced by drought stress. The overexpression of NF-Y7 and 10 causes a
dwarf phenotype which is highly adaptive in stress since NFY leads to growth retardation
because of lack of water and they also reduce CO2 assimilation as a stress response. Heat stress
transcription factor HsfA3 up-regulated in drought response since it is a potential inducer of
heat shock protein. However, the histone variants are exceptionally down regulated which
further leads to a limitation of DNA replication and produce dwarf plants. Therefore, the gene
expressions and physiological responses are interconnected and in response to the drought, all
gene expression suppressed. The similar kind of result observed when, Bechtold et al. (2016),
conducted Time-Series Transcriptomics study on Arabidopsis thaliana to reveal the chronology
that of plant responses to drought stress. The researches performed analysis of physiological,
metabolic and transcriptional changes in Arabidopsis. The result suggested that the stomatal
limitation is the primary factor which leads to the reduction of photosynthesis under mild
drought. The majority of transcription factors such as ABRE binding factor, NAC transcription
factors, and CCAAT binding proteins responded to late or terminal drought stress especially
those factors which are associated oxidative stress responses that further increase the tolerance
and regulate the plant development accordingly. These genes, especially AGL22, DREB1A, and

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FBH3 regulates ABA signalling which further inhibits the growth of root and shoot and
promotes seed dormancy. This pathway also confers tolerance to freezing through induction of
dehydration-tolerance gene. However, the researchers only focused on Arabidopsis to gain an
understanding of the stress response, highlighting selection bias. Further research is required to
explore the mechanism in other plants. On a different note, Chmielewska et al. (2016)
conducted proteomics and metabolomics study to explore the metabolic changes in the leaves
and roots of two barley plants with contrasting drought tolerance. The researchers undertook
two-dimensional electrophoresis combined with matrix-assisted laser desorption time of flight
mass spectrometry to analyse revealed 121 drought response protein in leaves as well as 182
proteins of roots for both genotypes The result suggested the significant minimization in
abundance of RubisCO large subunit and associated binding proteins. The researchers found a
constitute accumulation of the of HSP70s in the barley phenotypes which are more susceptible
to drought. The researchers also documented that elevated proline level enhances drought
tolerance when barley plants are subjected to drought. In stressed plants, the high accumulation
of the osmoprotective disaccharides and trisaccharides are observed which further induce
osmotic adjustments and stomatal disclosure. However, for this research also selection bias was
observed. Hong et al. (2016) undertook similar kinds of proteomics study such as comparison
of root cytoplasmic proteome in drought-tolerant rice. A total of 510 proteins spots were
observed after identification which induces drought response. These proteins involve in
bioenergy and mainly consist of malate dehydrogenase, succinyl co A and pyruvate
dehydrogenase. These proteins are significantly distributed when sudden water deficit observed
in the patient and shows senescence and short root growth. However, this distribution
contributed to strong drought tolerance capabilities which resulted in high grain production.

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Conclusion:
Thus concluded that drought stress is abiotic stress which affected the growth of plants
including their metabolism protein translations and other activities. This paper explored the
literature review to gain an understanding of the stress responses plants exhibit when subjected to
the drought stress. The result suggested that plants such as tomato exhibit overexpression of NF-
Y7 and 10 which further contribute to growth regulating, minimization of CO2 assimilations and
dwarf plant formation. Arabidopsis thaliana inhibit root a shoot inhibition through protein
expression, barely shows osmolar adjustment and stromal disclosure but in rice plant, the
improved growth tolerance shows senescence and short root growth.

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