The Art of Self-Control – Autoregulation of Plant–Microbe Symbioses

Abstract

Plants interact with diverse microbes including those that result in nutrient-acquiring symbioses. In order to balance the energy cost with the benefit gained, plants employ a systemic negative feedback loop to control the formation of these symbioses. This is particularly well-understood in nodulation, the symbiosis between legumes and nitrogen-fixing rhizobia, and is known as autoregulation of nodulation (AON). However, much less is understood about the autoregulation of the ancient arbuscular mycorrhizal symbioses that form between Glomeromycota fungi and the majority of land plants. Elegant physiological studies in legumes have indicated there is at least some overlap in the genes and signals that regulate these two symbioses but there are major gaps in our understanding. In this paper we examine the hypothesis that the autoregulation of mycorrhizae (AOM) pathway shares some elements with AON but that there are also some important differences. By reviewing the current knowledge of the AON pathway, we have identified important directions for future AOM studies. We also provide the first genetic evidence that CLV2 (an important element of the AON pathway) influences mycorrhizal development in a non-legume, tomato and review the interaction of the autoregulation pathway with plant hormones and nutrient status. Finally, we discuss whether autoregulation may play a role in the relationships plants form with other microbes.

Efecto de ácidos húmicos, micorrizas y quitosano en indicadores del crecimiento de dos cultivares de tomate (Solanum lycopersicum L.)

“…In this manner, ions, such as N, K + , Ca 2+ , and Mg 2+ increased signif icantly in both cultivars with the use of mycorrhizal fungi; however, their application had an opposite effect in the case of phosphorus concentration since a signif icant biomass decrease was observed. This result constituted a contradictory behavior because a notorious influence of arbuscular mycorrhizal fungi on plants is their role in solubilizing this element in soil, making it easier to be absorbed by the roots (Salvioli et al, 2012;Johri et al, 2015;Wang et al, 2018). In this case, the treatment with the most influence was humic acid in both cultivars used, which showed the greatest values.…”

“…de HMA (Cuadro 4). De esta forma, la concentración de iones como N, K + , Ca 2+ y Mg 2+ en los dos cultivares se incrementó de manera signif icativa con el uso de los hongos micorrízicos, sin embargo, la aplicación de estos tuvo un efecto contrario en el caso de la concentración de fósforo, debido a que esta manifestó un decrecimiento signif icativo en la biomasa, lo cual constituye un comportamiento contradictorio, pues una de las influencias más notorias de los hongos micorrízicos arbusculares sobre las plantas es su papel en la solubilización de este elemento en el suelo, poniéndolo de una forma asimilable para la absorción por las raíces (Salvioli et al, 2012;Johri et al, 2015;Wang et al, 2018). En este caso, el tratamiento de mayor influencia fue el ácido húmico en los dos cultivares usados, los cuales presentaron los mayores valores, sin embargo, no existieron diferencias notables con respecto a la aplicación de quitosano e incluso el control, lo cual evidencia que los bioproductos ejercieron muy poca influencia en la movilización de este elemento hacia la planta, debido a que las mismas en condiciones naturales fueron capaces de suplir sus necesidades en la nutrición fosfórica, probablemente por la alta disponibilidad de este elemento en el sustrato utilizado.…”

“…Varios bioestimulantes han sido estudiados tales como bacterias f ijadoras de nitrógeno, productos que mejoran la nutrición estimulan el crecimiento, desarrollo y rendimiento del cultivo (Agbodjato et al, 2016;Capstaff y Miller, 2018;Wang et al, 2018). Entre ellos destaca por su versatilidad para su aplicación en…”

“…Several bioestimulants have been studied, such as nitrogen-f ixing bacteria, products that improve nutrition stimulating growth, development and yield (Agbodjato et al, 2016;Capstaff and Miller, 2018;Wang et al, 2018). Among other biostimulants, chitosan, a biopolymer derived from chitin, stands out for its versatility in agriculture application stimulating plant growth (Barbosa et al, 2017;Chun and Chandrasekaran, 2018;Divya et al, 2018a).…”

The role of CLV1, CLV2 and HPAT homologs in nitrogen-regulation of root development

“…Secondly, elements of the CLV-CLE peptide pathway have been shown to be involved in mediating nitrogen response of roots. In legumes, this involves elements of the negative feedback autoregulation of nodulation (AON) pathway (reviewed by Wang et al 2018). In AON, CLE peptides are induced by rhizobia and/or high nitrogen and are perceived by LRR-RLK in Medicago truncatula, Lotus japonicus, soybean and pea (SUNN/HAR1/NARK/SYM29).…”