A. V. Sorokan

Structural-functional features of plant isoperoxidases.

Current data on structural-functional features of plant peroxidases and their involvement in functioning of the pro-/antioxidant system responding to stress factors, especially those of biotic origin, are analyzed. The collection of specific features of individual isoforms allows a plant to withstand an aggressive influence of the environment. Expression of some genes encoding different isoperoxidases is regulated by pathogens (and their metabolites), elicitors, and hormone-like compounds; specific features of this regulation are considered in detail. It is suggested that isoperoxidases interacting with polysaccharides are responsible for a directed deposition of lignin on the cell walls, and this lignin in turn is concurrently an efficient strengthening material and protects the plants against pathogens.

Regulation of peroxidase activity under the influence of signaling molecules and Bacillus subtilis 26D in potato plants infected with Phytophthora infestans

The influence of sequential application of 5 × 10−5 M salicylic acid (SA) or 1 × 10−7 M jasmonic acid (JA) and endophytic bacterium Bacillus subtilis strain 26D on peroxidase activity, transcription of the M21334 isoperoxidase gene from potato (Solanum tuberosum L.), and the formation of resistance to the infective agent of potato late blight Phytophthora infestans (Mont.) de Bary was studied. It was found that individual application of JA or Bacillus subtilis 26D and sequential application of SA and B. subtilis 26D were the most effective in protecting plants against pathogens, while sequential application of JA and B. subtilis 26D drastically suppressed plant resistance. The results suggest the need for strict compliance with regulations when using SA and JA, as well as biological products based on living bacteria as modern plant protection products with immunomodulatory properties that trigger specific signaling pathways, which often interfere with each other.

RNA silencing of the anionic peroxidase gene impairs potato plant resistance to Phytophthora infestans (Mont.) de Bary

Potato Solanum tuberosum L. plants expressing an antisense M21334 fragment were obtained by agrobacterial transformation. A manifold decrease in activity of anionic isoperoxidase with pI ∼ 3.5 in the transformed plants demonstrated that the enzyme is encoded by M21334. The transformed plants showed a decrease in lignin accumulation and a dramatically lower resistance to the late blight agent Phytophthora infestans, implicating the enzyme in the response to P. infestans infection.

Polysaccharide-Specific Isoperoxidases as an Important Component of the Plant Defence System

The plant cell wall is a very complex and dynamic system, similar in importance to both the extracellular and intracellular processes which are recognised nowadays. The cell wall is a “vanguard” an effective barrier in the way of different negative chemical and biotic factors, including pathogens and wounding. The defence functions of plant cell walls are associated with the construction of physical barriers consisting of ligninand suberincontaining polymers on the path of pathogens inside a plant. This reaction develops more or less automatically, and barriers are only formed in the zone of pathogen penetration during active pathogen expansion into the host plant’s tissues. Yet the mechanisms of these events are still unclear. It is well-known that peroxidases (PO) are key enzymes involved in lignification (Cosio & Dunand, 2009) and one of the few proteins secreted into the plant cell wall. However, POs have numerous applications in industry and one of the most important of these is the use of POs for lignin degradation. Therefore, both analytics and industry require a great volume of stable PO preparations of a high quality and at a low price, and the search for new methods and substrates for their extraction and purification has great commercial importance. Thus, the ability of plant oxidoreductases to interact with the biopolymers of the cell walls of plants and fungi has been studied for several decades (Siegel, 1957; McDougall, 2001). Moreover, it has been shown that plant POs can bind electrostatically with calcium pectate (Dunand et al., 2002) and chitin (Khairullin et al., 2000). Plants are likely to contain a whole subclass of these “polysaccharide-specific” isoPOs and their encoding genes. This subclass should be characterised by the ability to bind with polysaccharides and the defence function focused on strengthening the cell wall of the host and isolating the non-infected host tissues from the pathogen with the help of lignin. We suppose that the ability of plant POs to interact with some biopolymers without losing their activity can be applied for the isolation and purification of these enzymes. The possibility of the application of chitin in agriculture, biomedicine, biotechnology and the food industry has received much attention due to its biocompactibility, biodegradability and bioactivity. The low price and the ecological safety of this biopolymer define it as an available matrix for technological processes. As such, it may be possible to produce the high-quality preparations of POs that are needed for various fields of industry and analytical methods with the use of chitin (or other

Interaction between salicylate- and jasmonate-induced signal transduction pathways in the development of potato resistance to late blight with the involvement of peroxidase gene M21334

Effects of 50 μM salicylic acid (SA) and 0.1 μM jasmonic acid (JA) on the transcriptional activity of the genes encoding isoperoxidase (M21334) and PR-1 and PR-6 proteins during the development of potato (Solanum tuberosum L.) defense response to Phytophthora infestans (Mont.) de Bary were investigated. The considerable accumulation of transcripts of peroxidase M21334 gene occurred in infected plants treated with JA together with SA or after SA, but not in the case of SA after JA. A decrease of the area of lesions induced by P. infestans on potato leaves treated with these compounds is one of the indications of their stimulatory effects on plant immunity. The obtained data suggest that plant resistance to the late blight is regulated via systemic induced resistance where JA plays an important role as an intermediate on conditions of active regulatory participation of SA.

The Interplay Between Salicylic and Jasmonic Acid During Phytopathogenesis

There is no doubt that the salicylic acid (SA) plays an important role in plant defence against pathogens attacks. According to the established opinion, SA induces the systemic acquired resistance (SAR) that is effective defense against numerous biotrophic pathogens that colonize living plant tissue from where they consume nutrients, suppressing their immune response. SAR is largely due to programmed cell death and early oxidative burst in the host cells. In contrast, necrotrophic pathogens do not suffer from cell death and salicylic acid–dependent defenses. SA-induced cell death can promote development of pathogenic structures. Mechanisms of defence against necrotrophs are regulated by another set of defense responses activated by jasmonic acid (JA) and so-called induced systemic resistance (ISR). Literature data indicate that the signals inducing SAR or ISR are strictly individual: SA can antagonize JA signaling and vice versa. Probably, crosstalks between SA and JA help the plant to minimize fitness costs and create a flexible signaling network that allow the plant to regulate its defense responses against invaders. However, there are some data evidencing certain synergy or additive effect of SA on processes attributed to ISR. This article is focused on some aspects of interplay of SA with JA during the establishment of plant resistance to pathogens with different type of nutrition and participation of peroxidases in this process.

The influence of potato endophytes on Leptinotarsa decemlineata endosymbionts promotes mortality of the pest.

Plants are exposed to pervasive attack by diverse attackers, such as pathogens and pests. But plants have their own endophytic microflora as well as the attacking insects. These microbiomes contact face to face in the nature. It has been found that the endophytic strain Bacillus subtilis 26D increases mortality of Colorado potato beetles, disturbing the development of insect microsymbionts Enterobacter ssp. and Acinetobacter ssp.