RESUMEN
Beneficial endophytic bacteria can suppress the development of insect pests through direct antagonism, with the help of metabolites, or indirectly by the induction of systemic resistance through the regulation of hormonal signaling pathways. Lipopeptides are bacterial metabolites that exhibit direct antagonistic activity against many organisms, including insects. Also, lipopeptides are able to trigger induced systemic resistance (ISR) in plants against harmful organisms, but the physiological mechanisms of their action are just beginning to be studied. In this work, we studied ten strains of bacteria isolated from the tissues of wheat and potatoes. Sequencing of the 16S rRNA gene showed that all isolates belong to the genus Bacillus and to two species, B. subtilis and B. velezensis. The genes for lipopeptide synthetase - surfactin synthetase (Bs_srf ), iturin synthetase (Bs_ituA, Bs_ituB) and fengycin synthetase (Bs_fenD) - were identified in all bacterial isolates using PCR. All strains had high aphicidal activity against the Greenbug aphid (Schizaphis graminum Rond.) due to the synthesis of lipopeptides, which was proven using lipopeptide-rich fractions (LRFs) isolated from the strains. Endophytic lipopeptide-synthesizing strains of Bacillus spp. indirectly affected the viability of aphids, the endurance of plants against aphids and triggered ISR in plants, which manifested itself in the regulation of oxidative metabolism and the accumulation of transcripts of the Pr1, Pr2, Pr3, Pr6 and Pr9 genes due to the synthesis of lipopeptides, which was proven using LRF isolated from three strains: B. subtilis 26D, B. subtilis 11VM, and B. thuringiensis B-6066. We have for the first time demonstrated the aphicidal effect of fengycin and the ability of the fengycin-synthesizing strains and isolates, B. subtilis Ttl2, Bacillus sp. Stl7 and B. thuringiensis B-6066, to regulate components of the pro-/antioxidant system of aphid-infested plants. In addition, this work is the first to demonstrate an elicitor role of fengycin in triggering a systemic resistance to S. graminum in wheat plants. We have discovered new promising strains and isolates of endophytes of the genus Bacillus, which may be included in the composition of new biocontrol agents against aphids. One of the criteria for searching for new bacteria active against phloem-feeding insects can be the presence of lipopeptide synthetase genes in the bacterial genome.
RESUMEN
The influence of sequential exposure of 5 x 10(-5) M salicylic acid (SA) or 1 x 10(-7) M jasmonic acid (JA) and endophytic bacterium Bacillus subtilis strain 26D on peroxidase activity, transcription of the M21334 isoperoxidase gene from potato (Solarium tuberosum L.), and the formation of resistance to the infective agent of potato 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.
Asunto(s)
Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Peroxidasa/genética , Reguladores del Crecimiento de las Plantas/farmacología , Proteínas de Plantas/genética , Solanum tuberosum/genética , Bacillus subtilis/fisiología , Agentes de Control Biológico , Ciclopentanos/farmacología , Oxilipinas/farmacología , Peroxidasa/metabolismo , Phytophthora infestans/crecimiento & desarrollo , Phytophthora infestans/patogenicidad , Enfermedades de las Plantas/genética , Enfermedades de las Plantas/microbiología , Proteínas de Plantas/metabolismo , Ácido Salicílico/farmacología , Transducción de Señal/efectos de los fármacos , Solanum tuberosum/efectos de los fármacos , Solanum tuberosum/enzimología , Solanum tuberosum/microbiología , Transcripción Genética/efectos de los fármacosRESUMEN
Transformed potato (Solanum tuberosum L.) plants expressing the antisense-fragment of M21334 gene were estimated. In transgenic plants the decrease of anionic isoperoxidase pI - 3.5 activity was detected. So, the data testify that M21334 gene encodes this isoperoxidase. Decrease of lignin accumulation and dramatic decline of resistance of transgenic potato plants to the late blight agent Phytophthora infestans emphasize an importance of isoperoxidase pI - 3.5 in defense reaction against late blight.
Asunto(s)
Peroxidasas/genética , Phytophthora infestans/patogenicidad , Solanum tuberosum/genética , Solanum tuberosum/microbiología , Pared Celular/metabolismo , Pared Celular/microbiología , Interacciones Huésped-Patógeno , Lignina/metabolismo , Peroxidasas/metabolismo , Enfermedades de las Plantas/genética , Enfermedades de las Plantas/microbiología , Plantas Modificadas Genéticamente , Interferencia de ARN , Solanum tuberosum/enzimologíaRESUMEN
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.