Overexpression of IRM1 Enhances Resistance to Aphids in Arabidopsis thaliana

Abstract

Aphids are insects that cause direct damage to crops by the removal of phloem sap, but more importantly they spread devastating viruses. Aphids use their sophisticated mouthpart (i.e. stylet) to feed from the phloem sieve elements of the host plant. To identify genes that affect host plant resistance to aphids, we previously screened an Arabidopsis thaliana activation tag mutant collection. In such mutants, tagged genes are overexpressed by a strong 35S enhancer adjacent to the natural promoter, resulting in a dominant gain-of-function phenotype. We previously identified several of these mutants on which the aphid Myzus persicae showed a reduced population development compared with wild type. In the present study we show that the gene responsible for the phenotype of one of the mutants is At5g65040 and named this gene Increased Resistance to Myzus persicae 1 (IRM1). Overexpression of the cloned IRM1 gene conferred a phenotype identical to that of the original mutant. Conversely, an IRM1 knockout mutant promoted aphid population development compared to the wild type. We performed Electrical Penetration Graph analysis to investigate how probing and feeding behaviour of aphids was affected on plants that either overexpressed IRM1 or contained a knockout mutation in this gene. The EPG results indicated that the aphids encounter resistance factors while reaching for the phloem on the overexpressing line. This resistance mechanism also affected other aphid species and is suggested to be of mechanical nature. Interestingly, genetic variation for IRM1 expression in response to aphid attack was observed. Upon aphid attack the expression of IRM1 was initially (after 6 hours) induced in ecotype Wassilewskija followed by suppression. In Columbia-0, IRM1 expression was already suppressed six hours after the start of the infestation. The resistance conferred by the overexpression of IRM1 in A. thaliana trades off with plant growth.

The FCS-like zinc finger scaffold of the kinase SnRK1 is formed by the coordinated actions of the FLZ domain and intrinsically disordered regions

“…In agreement with this, FLZ proteins were found to be interacting with regulators of hormone signaling, with development and abiotic and biotic stresses supporting their role as adaptors to mediate SnRK1 signaling (8,10). Functional analysis of FLZ genes identified their roles in the regulation of many SnRK1-regulated processes (11)(12)(13). Consistent with these studies, we recently identified that two members of Arabidopsis FLZ gene family work as negative regulators of SnRK1 signaling (14).…”

Molecular Characterization of Rice OsLCB2a1 Gene and Functional Analysis of its Role in Insect Resistance

“…For instance over-expression of Increased Resistance to Myzus persicae 1 ( IRM1 ) gene might result in mechanical barriers that reduces the population size of M . persicae in A. thaliana (Chen et al, 2013). Likewise, the aphid population size was smaller in transgenic plants, overexpression of cotton photosynthesis-related gene GhPSAK1 suggesting that GhPSAK1 might improve aphid-tolerance of the transgenic plants (Zhang et al, 2014).…”

“…These findings can be supported by the relevant previous studies. For example Chen et al (2013) hypothesized that over-expression of IRM1 interrupted the capability of M. persicae to reach sustained phloem sap ingestion and the tested aphids needed double the time compared to the WT. Over-expression of SKU5 SIMILAR 13 ( SKS13 ) in A. thaliana led to a reduced phloem feeding of M. persicae , which was probably due to accumulation of ROS in leaves.…”

FCS‐like zinc finger 6 and 10 repress SnRK1 signalling in Arabidopsis

“…The expression of FLZ genes is highly regulated by energy status and abiotic stress (Jamsheer K and Laxmi, ). Functional analyses identified that FLZ proteins are involved in the regulation of abiotic stress, ABA‐responses and growth and development (He and Gan, ; Chen et al ., ; Hou et al ., ). The transcriptional regulation of FLZ genes by sugars and the interaction of FLZ proteins with kinase subunits of SnRK1 suggest that their role in plant growth and stress adaptation is possibly mediated through the interaction with SnRK1 signalling.…”