<div>Autophagy is a basically survival mechanism of body in which cell digests its own content to maintain cellular homeostasis in multiple stress conditions and starvation. The term &lsquo;autophagy&rsquo; was first described in 1963 by Christian de Duve, a Japanese cell biologist to describe presence of double-membrane vesicles containing cytoplasmic constituents within the cell. These vesicles that encapsulate cytoplasm, organelles and proteins, are known as autophagosomes. After formation of autophagosome it fuses with endosomes and travels via cytoplasm to fuse with lysosomes for degradation. In lysosomes internal content material of autophagosome is degraded with the action of acid hydrolases. Autophagy is very important for regulation of diverse cellular functions i.e., growth, differentiation, response to nutrient deficit and oxidative stress, cell death and macromolecule and organelle turnover. Nutrient starvation is most typical trigger of autophagy. Depending on the mechanism by which intracellular materials are delivered into lysosome for degradation, there are four types- Macroautophagy, Microautophagy, Chaperon mediated autophagy and Crinophagy. Autophagy is important in normal development and it responds to changing environmental stimuli. It plays role in cancer and numerous important diseases such as bacterial and viral infections, liver and kidney diseases, Diabetes mellitus, inflammatory bowel diseases, neurodegenerative disorders, several myopathies and cardiovascular diseases.</div>


<p>Autophagy A Cellular Mechanism: A Review</p>


<div style="text-align: justify;">Hypersensitivity is a natural defense for plants in response to a variety of pathogens such as viruses, bacteria, fungi and is characterized by a programmed cell death (PCD) accompanied by an accumulation of toxic compounds within the dead cell. Hypersensitive response (HR) is considered a biochemical reaction rather than a structural defense mechanism but can be seen with the naked eye or with a microscope. There are two types of hypersensitive responses: structural and induced. PCD is seen in both structural as well as in induced hypersensitive response. PCD is extreme resistance shown by the plants in which it kills its cells (suicidal death), upon a perception of the pathogen to deprive it of nutritional supply and stops its growth. Cell death plays a central role in innate immune responses in both plants and animals. Apoptosis and autophagy are physiological processes and two forms of biochemical PCD. Induced hypersensitive response comes out when the plant recognizes specific pathogen-produced signal molecules known as elicitors. Recognition of elicitors by the host plants activates an army of biochemical reactions. These reactions include an oxidative burst of reactive oxygen species (ROS), alterations in plant cell wall also including cell wall immunity (CWI) and damage-associated molecular patterns (DAMPs), induction of phytoalexins and synthesis of PR proteins. These all, are comprised under the first line of defense of plants which come into action after recognition of conserved molecules characteristic of many microbes. These are called elicitors and are known as microbeassociated or pathogen-associated molecular patterns (MAMPs or PAMPs). The second line of defense of plants is the recognition of effectors through plant resistance gene products known as R genes, which result in effector-triggered immunity (ETI). This is supported by the gene for gene hypothesis. Avirulence gene encodes a protein which is specifically recognized by genotypes of the host plant harboring the matching resistance genes.</div>

Autophagy A Cellular Mechanism: A Review

Hypersensitive Responses in Plants