001. Sherien Bukhat, Asma Imran, Shaista Javaid, Muhammad Shahid, Afshan Majeed, TahirNaqqash. Institute of Molecular Biology and Biotechnology, Bahauddin Zakariya University, 60800 Multan, Pakistan. Communication of plants with microbial world: Exploring the regulatory networks for PGPR mediated defense signaling. Microbiological Research, 2020, 238, Pages: 126486.

      Agricultural manipulation of potentially beneficial rhizosphere microbes is increasing rapidly due to their multi-functional plant-protective and growth related benefits. Plant growth promoting rhizobacteria (PGPR) are mostly non-pathogenic microbes which exert direct benefits on plants while there are rhizosphere bacteria which indirectly help plant by ameliorating the biotic and/or abiotic stress or induction of defense response in plant. Regulation of these direct or indirect effect takes place via highly specialized communication system induced at multiple levels of interaction i.e., inter-species, intra-species, and inter-kingdom. Studies have provided insights into the functioning of signaling molecules involved in communication and induction of defense responses. Activation of host immune responses upon bacterial infection or rhizobacteria perception requires comprehensive and precise gene expression reprogramming and communication between hosts and microbes. Majority of studies have focused on signaling of host pattern recognition receptors (PRR) and nod-like receptor (NLR) and microbial effector proteins under mining the role of other components such as mitogen activated protein kinase (MAPK), microRNA, histone deacytylases. The later ones are important regulators of gene expression reprogramming in plant immune responses, pathogen virulence and communications in plant-microbe interactions. During the past decade, inoculation of PGPR has emerged as potential strategy to induce biotic and abiotic stress tolerance in plants; hence, it is imperative to expose the basis of these interactions. This review discusses microbes and plants derived signaling molecules for their communication, regulatory and signaling networks of PGPR and their different products that are involved in inducing resistance and tolerance in plants against environmental stresses and the effect of defense signaling on root microbiome. We expect that it will lead to the development and exploitation of beneficial microbes as source of crop biofertilizers in climate changing scenario enabling more sustainable agriculture.

Keywords: Plant growth promoting bacteria, Defense signaling, Systemic acquired resistance, Induced systemic resistance, Plant microbe communication, Signaling molecules.

002. Michelle Eafkhami, Brianna Kalmeida, Damian Jhernandez, Kasey N Kiesewetter, Daniel Previllini. University of Miami, Department of Biology, Coral Gables, FL 33146, USA. Tripartite mutualisms as models for understanding plant–microbial interactions. Current Opinion in Plant Biology, 2020, 56, Pages 28 - 36.

      All plants host diverse microbial assemblages that shape plant health, productivity, and function. While some microbial effects are attributable to particular symbionts, interactions among plant-associated microbes can nonadditively affect plant fitness and traits in ways that cannot be predicted from pairwise interactions. Recent research into tripartite plant–microbe mutualisms has provided crucial insight into this nonadditivity and the mechanisms underlying plant interactions with multiple microbes. Here, we discuss how interactions among microbial mutualists affect plant performance, highlight consequences of biotic and abiotic context-dependency for nonadditive outcomes, and summarize burgeoning efforts to determine the molecular bases of how plants regulate establishment, resource exchange, and maintenance of tripartite interactions. We conclude with four goals for future tripartite studies that will advance our overall understanding of complex plant–microbial interactions.

Keywords: tripartite plant–microbe, highlight consequences of biotic and abiotic context-dependency, tripartite interactions, plant–microbial interactions.