FORMATION OF PLANTS NONSPECIFIC INDUCED IMMUNITY AT THE BIOGENOUS STRESS (review)

Because of pesticide pollution and violation of protective reactions in biosystems, the ways to increase a nonspecific natural resistance in plants is relevant. For the recent decades the mechanisms of pathogens-to-plant cell interaction were revealed. To identify chemical signals arising in the spots of plant infection by pathogenic microorganisms, the term «elicitor» was suggested (M. Yoshikawa et al., 1993; M. Thakur et al., 2013). Cell innate immunity is based on the recognition of phytopathogenic surface molecules, which is a primary signal for actuating the complicated network, including induction and phytoimmunity regulation (I. Tarchevskii, 2000). During signaling the essential role is played by proteins and small molecule messengers (salicylic acid and jasmonic acid, hydrogen peroxide, nitric oxide). Salicylic acid is involved in amplification and multiplication of the signals coming from the receptors into the plant cells, which ensures the timely activated protection. The earliest plant organism response to the pathogen introduction is a local generation of reactive oxygen species (oxidative burst), triggering a chain of subsequent defense mechanisms (S. Tyuterev, 2002). A significant increase in the level of reactive O2 and H2O2 has an inhibitory effect on the pathogenic microorganisms. The reactive oxygen species (ROS) are also suggested to play significant role in the membrane lypooxidation, cell wall modification and signal transduction (C. Richael et al., 1999; T. Pietras et al., 1997). A key role in ROS regulation is played by an antioxidant defense system, which function is to slow down and prevent intracellular oxidation of organic substances. In this, the antioxidant enzymes (superoxide dismutase, catalase, peroxidase) and low molecular weight antioxidants (ascorbic acid, glutathione, tocopherol, carotenoids, anthocyanins) are mainly involved (S.S. Gill et al., 2010). A defensive effect of peroxidases is due to oxidation of phenolic compounds to quinones (B. Barna et al.; 1995, E.N. Okey et al., 1997). The correlation was found between peroxidase activity in plant tissues and plant resistance to pathogens (T.B. Kumeiko et al., 2009; N. Radhakrishnan et al., 2009). An increase in catalase activity is a defense reaction in cells during the next stages of biotic stress development (F.M. Shakirova, 2001). Starting from reception of signaling molecules of phytopathogens on the cell membrane all metabolic processes are controlled by resistance genes that regulate complex defense reactions (V. Repka et al., 2004). As a consequence, plants produce large variety of substances, carrying protection functions. The main ones are phytoalexins and PR-proteins (Yu. D’jakov, 2012). Due to stress proteins, the enzymes get activated, the membrane stabilization occurs, the activity of mitochondria and chloroplasts increases, and, therefore, the energy level rises (T. Chirkova, 2002). The data summarized herein are the basis for developing new concept for protection of agricultural crops by means of biologicals with eliciting effect that boost plant immune state.