Plant Physiology - Musiyenko M.M. 2001

Adaptation and plant stress resistance mechanisms
The nature of adaptive rearrangements in the synthesis and degradation of biopolymers under stress conditions

Stress Proteins. Significant recent progress in understanding the MOLECULAR MECHANISMS OF adaptive responses is attributed to advances in research on macromolecule Synthesis and degradation under stress conditions. Processes occurring at the transcriptional and post-transcriptional levels, as well as biopolymer degradation and interactions between various Cell compartments, are highly sensitive to environmental changes.

The response of the genetic apparatus to environmental changes was first discovered in the 1960s with the detection of heat Shock protein (HSP) synthesis induced by high temperatures. It turned out that specific Polypeptides, normally absent, are synthesized in response to various factors (Temperature, humidity, salinity, heavy metals, oxygen, etc.). Such proteins are termed stress proteins, and it became clear that their biosynthetic potential is a universal biological phenomenon.

In the 1970s, it was proven that Gene Expression and the pattern of Protein Synthesis under stress in plants are analogous to those in other organisms. Gene expression under these conditions is a rapid response; just a few minutes of exposure to adverse conditions is sufficient to reorganize the genetic machinery to ensure the informational capacity for stress protein synthesis. Concurrently, the METABOLISM/31.html">Transcription of the total mRNA population required for normal metabolic Protein synthesis is partially or completely suppressed. It should be noted that stress proteins are synthesized in small amounts, typically up to 2% of normal protein content.

The synthesis of stress proteins is transient, observed for several hours following the onset of the stress factor, and typically occurs in two stages: first, a group of so-called early proteins is formed, followed by late proteins.

The only difference in genome expression between Higher Plants and other organisms is that only in plants has a group of polypeptides with a relatively low molecular mass of 15–18 kDa been found. The pattern of polypeptide production largely depends on the duration of the stress factor, as well as the severity and rate of its change (Musienko, 1985). Interestingly, the synthesis of stress Proteins can also be determined by the specific Nature of the adverse impact. For example, among the stress proteins synthesized under elevated temperature and Water deficit, some are characteristic of both factors combined, while others are specific to only one of these stress states.

Among the proteins induced by A wide variety of stress factors, a polypeptide with a molecular mass of 70 kDa stands out, its gene being characterized by significant evolutionary conservation. Regardless of The Nature of the stress factor, de novo synthesized proteins have been identified in all cell compartments. It is believed that during their brief existence, stress proteins likely perform a protective or adaptive function. Thus, transcription processes—particularly those associated with mRNA synthesis and fate—exhibit high sensitivity to environmental fluctuations. It is hypothesized that a portion of untranslated mRNA, along with some translated mRNAs, may be preserved as so-called stress granules, which are ribonucleoprotein complexes.