Agriculture Reference
In-Depth Information
During the last decade, our research groups have focused their research on elucidating the
different components and molecular players underlying abiotic stress responses of a broad
range of species both model and crops plant. Several attempts to engineer those species with
improved abiotic stress traits (drought and salinity) were made and the response of genetically
engineered plants was deeply studied after establishment of adequate physiological methods.
Now, we are moving efforts to expand our knowledge on plants response to abiotic stresses
using holistic System Biology approaches, taking advantage of available high throughput tools
such as transcriptomics, proteomics and metabolomics.
The aim of this chapter is to provide a general overview of the main studies made and how
the different expertises of our team were pooled to improve our understanding of the biology
of abiotic stress responses in plants. We present some details about the main results and
perspectives regarding other possible approaches to develop plants better adapted to face the
environmental constraints.
2. Physiological mechanisms underlying abiotic stress responses
Stress is a concept imported from physics. It was introduced in the theory of elasticity as the
amount of force for a given unit area [10]. In a biological context, stress is usually defined as
an external factor that exerts a disadvantageous influence on the plant [11]. Alternatively, stress
could be defined as a significant deviation of the optimal condition of life [12].
2.1. Physiological responses to early abiotic stress: Functional decline in the alarm phase —
The stress reaction
Three main phases may be considered on plant stress events and responses: i) the phase of
alarm; ii) the phase of resistance; and iii) the phase of exhaustion [12]. Lichtenthaler [13] added
a fourth phase, the regeneration phase, which occurs only when the stressor is removed before
damage being too severe, allowing partial or full regeneration of the physiological functions.
The alarm phase starts with the so-called stress reaction, characterized by functional declines
due to the stressor factor, offset by restitution counter reactions, in the transition to the phase
of resistance. Stressors rarely act separately and individually on a plant. Generally, several
stress factors act simultaneously, such as the frequently combined, at sunny, warm and dry
summer periods, heat, water and high-light stress [14].
Sensing is the very first event experienced by a plant when one or more environmental factors
(biotic or abiotic) depart from their optimum. Stress sensing is a complex issue and there is not
a single sensing mechanism common to all stresses. For instance, some stresses directly affect
the underground parts of plant bodies (e.g. drought, flooding) whereas other stresses (e.g.,
photoinbition) affect directly the aboveground structures of plant bodies. It is, thereby,
expected that different sensing mechanisms will be involved. The most common model of
sensing external stimuli is that of a chemical ligand binding to a specific receptor [15]. This
model, however, is suitable only for chemical stresses (e.g., heavy metal stress, nutrient
depletion stress), not for physical stresses: primary sensing of temperature stress (heat stress
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