Microbial lipo-chitooligosaccharides as key regulators of plant growth: Recent updates

Chemical fertilization is a favorite method of providing plants with their essential nutrients by farmers. However, due to being subject to leaching and emission of greenhouse gases, the complementary methods of fertilization such as biological ones (i.e. plant-microbes associations) may be economically and environmentally recommendable. During initiation of intimate associations between plants and soil microbes, a set of organic molecules including phenolic compounds such as flavonoids and lipo-chitooligosaccharides (LCOs) are exchanged between symbionts resulting in establishment and development of symbiosis. Due to competition with indigenous soil microbes, microbial inoculants including rhizobium and arbuscular mycorrhizal fungi may not be as efficient. So, interestingly, researchers have used organic molecules including bacterial LCOs, which can positively affect plant growth and yield production. However, more has to be indicated on related mechanisms including identification and expression of related genes in plant and bacteria. The present review article is about some of the most recent in LCOs production, effectiveness, compatibility and marketing. It also has reviewed and analysed how LCOs: 1) are produced by bacteria and mycorrhizal fungi, 2) are perceived by plant, 3) affect plant growth including the roots, 4) may act in stress conditions, and 5) affect climate change. LCOs and soil physicochemical properties are among the most important factors affecting the efficiency and so LCOs commercial production. Such analyses are useful for the development of microbial strains and species with high and effective LCOs production, which can efficiently enhance the growth and yield of legumes and non-legumes and are beneficial for environment.