Advances in the Xoo-rice pathosystem interaction and its exploitation in disease management

Bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the devastating diseases of riceworldwide. The pathogen reported to cause 70% crop loss in some of the susceptible genotypes under diseasefavoring environments, viz., temperature ranging between 25 to 34C and relative humidity more than 70%. InXoo, about 245 genes govern the pathogenicity and host specificity. The hypersensitive response andpathogenicity (hrp) genes responsible for disease occurrence were clustered in the pathogenicity island of 31.3Kb. The protein secreted through type three secretory system and type one secretory system mediates infectionand establishment of the pathogen inside the host. However, elicitor molecules from Xoo triggered the resistantresponse in rice against the pathogen. An array of resistant genes (R genes) was known to be invoked by thehost to combat the bacterial infection. To date, of the 45 Xa genes in rice, nine were cloned and characterized.The evolution of new races has made the task of developing resistant rice genotypes more challenging as itdemands a comprehensive breeding strategy involving the best use of R genes from the existing gene pool.Thus, to combat the infection from the existing races and to slow down the emergence of new Xoo races,pyramiding two or more R genes was found to be effective against bacterial blight disease. In India, thesuccessfully commercialized example includes the development of rice genotypes, viz., Improved Pusa Basmati-1, Improved Samba Mahsuri, PR106, Type 3 Basmati, and Mahsuri with selected R genes, viz., xa5, Xa4,xa13 and Xa21 against bacterial blight resistance. This review primarily portray Xoo-rice interactions andprovides opportunities for its effective management through sustainable technologies.

Transcriptomic profiling against Globodera pallida in resistant and susceptible potato roots / Perfil del transcriptoma de raíz de papa resistente y susceptible a Globodera pallida

Abstract Globodera pallida is a white potato cyst nematode present in the Andes, which causes huge losses to Peruvian farmers. An RNA-seq analysis allowed the identification of candidate genes that could mediate resistance against this pathogen. Two varieties, "María Huanca" (Solanum andigena) clone resistant (CIP 279142.12) and "Chimbina Colorada" (Solanum chaucha) (CIP 701013) clone susceptible to G. pallida, were used to identify differentially expressed genes. Total RNA from roots was extracted 72 hours post inoculation with second stage juveniles. Sequencing was done using the Illumina Hiseq 2500 platform. Reads were screened for quality issues and then mapped to the reference potato genome (clone DM1-3516 R44 v4.03). Here, we report 27717 and 27750 genes expressed in the resistant and susceptible variety respectively. The comparative analysis of expression identified 100 candidate genes. 91 genes were associated with resistance to G. pallida with Fold Change ≥ 2 (p <0.05). The remaining 9 R genes had Fold Change ≤ 1. We show differences in the expression of an NBS-LRR protein similar to Gro1-8, genes linked to late blight and TMV virus resistance.

Resumen Globodera pallida es un nemátodo formador de quistes. En la papa (Solanum tuberosum) ocasiona daños atrofiando las raíces. En los Andes peruanos ocasiona grandes pérdidas económicas a los agricultores. A través del análisis por RNA-seq, se identificaron genes candidatos que podrían mediar la resistencia contra este nemátodo. Dos variedades de papa: "María Huanca" (S. andigena) clon resistente (CIP 279142.12) y "Chimbina Colorada" (S. chaucha) clon susceptible (CIP 701013) a G. pallida, fueron utilizados para identificar genes expresados diferencialmente. Las raíces fueron inoculadas con G. pallida en segundo estadío juvenil (J2). El ARN total fue extraído a 72 horas post inoculación. El secuenciamiento fue realizado en plataforma Illumina HiSeq 2500. Las lecturas de buena calidad fueron mapeadas al genoma de referencia de S. tuberosum (clon DM1-3516 R44 v4.03). Reportamos 27717 y 27750 genes expresados en la variedad resistente y susceptible, respectivamente. El análisis comparativo identificó 100 genes candidatos, de ellos 91 genes fueron asociados con la resistencia a G. pallida (Fold Change ≥ 2 , p <0.05) y los 9 restantes con genes R ( Fold Change ≤ 1). En este último grupo se observaron diferencias en la expresión de genes NBS-LRR similar a Gro 1-8, genes relacionados a late blight y resistencia al Virus TMV.

Role of S gene product of bacteriophage lambda in host cell lysis.

Studies with the induced lysogens of λ S+R+, λS–R+, λS+R– and λS–R– phages have shown that while the S gene product is essential for the action of intracellular R gene product to release the periplasmic alkaline phosphatase in the presence of EDTA, the latter gene product can bring about this effect while acting on Escherichia coli cells from outside, in the absence of functional S gene product; chloroform, could help the intracellular R gene product in effecting bacterial lysis in the absence of S gene product. These result support the premise that the S gene product facilitates the R gene product in crossing the cytoplasmic membrane into the periplasmic space such that the latter can act on the peptidoglycan layer of the host cell thus causing both the release of alkaline phosphatase and cell lysis.