Aberrant growth and lethality of Arabidopsis deficient in nonsense-mediated RNA decay factors is caused by autoimmune-like response

Abstract

Nonsense-mediated RNA decay (NMD) is an evolutionarily conserved RNA quality control mechanism that eliminates transcripts containing nonsense mutations. NMD has also been shown to affect the expression of numerous genes, and inactivation of this pathway is lethal in higher eukaryotes. However, despite relatively detailed knowledge of the molecular basis of NMD, our understanding of its physiological functions is still limited and the underlying causes of lethality are unknown. In this study, we examined the importance of NMD in plants by analyzing an allelic series of Arabidopsis thaliana mutants impaired in the core NMD components SMG7 and UPF1. We found that impaired NMD elicits a pathogen defense response which appears to be proportional to the extent of NMD deficiency. We also demonstrate that developmental aberrations and lethality of the strong smg7 and upf1 alleles are caused by constitutive pathogen response upregulation. Disruption of pathogen signaling suppresses the lethality of the upf1-3 null allele and growth defects associated with SMG7 dysfunction. Interestingly, infertility and abortive meiosis observed in smg7 mutants is not coupled with impaired NMD suggesting a broader function of SMG7 in cellular metabolism. Taken together, our results uncover a major physiological consequence of NMD deficiency in Arabidopsis and revealed multifaceted roles of SMG7 in plant growth and development.

A physical, genetic and functional sequence assembly of the barley genome

“…2d and Table 2), similar to the percentage of nonsense-mediated decay (NMD)-controlled genes in a wide range of species 33,34 . Premature termination codons activate the NMD pathway 35 , which leads to rapid degradation of PTC1 transcripts, and have been associated with transcriptional regulation during disease and stress response in human and Arabidopsis, respectively 34,[36][37][38][39] . The distribution of PTC1 transcripts was strikingly dissimilar, both spatially and temporally, with only 7.4% shared and between 31% and 40% exclusively observed in only a single sample (Fig.…”

Alternative Splicing at the Intersection of Biological Timing, Development, and Stress Responses

“…In Arabidopsis, mutants in the homologs of the NMD components UP FRAMESHIFT1 (UPF1), UPF2, UPF3, and SMG7 show a higher resistance to P. syringae infection (Jeong et al, 2012;Rayson et al, 2012;Riehs-Kearnan et al, 2012;Shi et al, 2012). Among genes misexpressed in the upf1-5 and upf3-1 mutants, genes connected to pathogen response are enriched.…”

“…One may envisage that PTC-containing transcripts encoding putative truncated R gene products are stabilized for defense by downregulation of the NMD pathway. Clearly, a more detailed analysis is required to disentangle causes and consequences of the phenotypes: whether the increased level of defense-associated transcripts is due to an inhibition of mRNA degradation or an indirect consequence of elevated salicylic acid (SA) level in the mutants (Jeong et al, 2012;Rayson et al, 2012;Riehs-Kearnan et al, 2012).…”

BnaC9.SMG7b functions as a positive regulator of number of seeds per silique in rapeseed (Brassica napus L.) by regulating the formation of functional female gametophytes

“…Other than the function in progression out of meiosis II, AtSMG7 is also involved in the NMD, one of the approaches to eliminate the transcripts containing premature termination codon (PTC; Riehs et al, 2008;Riehs-Kearnan et al, 2012). To identify whether BnaC9.…”