Overexpressing components of the nuclear transport apparatus causes severe growth symptoms in tobacco leaves

Pilot-scale genome-wide association mapping in diverse sorghum germplasms identified novel genetic loci linked to major agronomic, root and stomatal traits

This genome-wide association studies (GWAS) used a subset of 96 diverse sorghum accessions, constructed from a large collection of 219 accessions for mining novel genetic loci linked to major agronomic, root morphological and physiological traits. The subset yielded 43,452 high quality single nucleotide polymorphic (SNP) markers exhibiting high allelic diversity. Population stratification showed distinct separation between caudatum and durra races. Linkage disequilibrium (LD) decay was rapidly declining with increasing physical distance across all chromosomes. The initial 50% LD decay was ~ 5 Kb and background level was within ~ 80 Kb. This study detected 42 significant quantitative trait nucleotide (QTNs) for different traits evaluated using FarmCPU, SUPER and 3VmrMLM which were in proximity with candidate genes related and were co-localized in already reported quantitative trait loci (QTL) and phenotypic variance (R2) of these QTNs ranged from 3 to 20%. Haplotype validation of the candidate genes from this study resulted nine genes showing significant phenotypic difference between different haplotypes. Three novel candidate genes associated with agronomic traits were validated including Sobic.001G499000, a potassium channel tetramerization domain protein for plant height, Sobic.010G186600, a nucleoporin-related gene for dry biomass, and Sobic.002G022600 encoding AP2-like ethylene-responsive transcription factor for plant yield. Several other candidate genes were validated and associated with different root and physiological traits including Sobic.005G104100, peroxidase 13-related gene with root length, Sobic.010G043300, homologous to Traes_5BL_8D494D60C, encoding inhibitor of apoptosis with iWUE, and Sobic.010G125500, encoding zinc finger, C3HC4 type domain with Abaxial stomatal density. In this study, 3VmrMLM was more powerful than FarmCPU and SUPER for detecting QTNs and having more breeding value indicating its reliable output for validation. This study justified that the constructed subset of diverse sorghums can be used as a panel for mapping other key traits to accelerate molecular breeding in sorghum.

Function of Nuclear Pore Complexes in Regulation of Plant Defense Signaling

In eukaryotes, the nucleus is the regulatory center of cytogenetics and metabolism, and it is critical for fundamental biological processes, including DNA replication and transcription, protein synthesis, and biological macromolecule transportation. The eukaryotic nucleus is surrounded by a lipid bilayer called the nuclear envelope (NE), which creates a microenvironment for sophisticated cellular processes. The NE is perforated by the nuclear pore complex (NPC), which is the channel for biological macromolecule bi-directional transport between the nucleus and cytoplasm. It is well known that NPC is the spatial designer of the genome and the manager of genomic function. Moreover, the NPC is considered to be a platform for the continual adaptation and evolution of eukaryotes. So far, a number of nucleoporins required for plant-defense processes have been identified. Here, we first provide an overview of NPC organization in plants, and then discuss recent findings in the plant NPC to elaborate on and dissect the distinct defensive functions of different NPC subcomponents in plant immune defense, growth and development, hormone signaling, and temperature response. Nucleoporins located in different components of NPC have their unique functions, and the link between the NPC and nucleocytoplasmic trafficking promotes crosstalk of different defense signals in plants. It is necessary to explore appropriate components of the NPC as potential targets for the breeding of high-quality and broad spectrum resistance crop varieties.

Structural and functional insight into the nuclear pore complex and nuclear transport receptors in plant stress signaling

Nuclear pore complexes (NPC) are highly conserved mega protein complexes that penetrate the double-layered nuclear membrane and form channels to allow bi-directional transport of macromolecules between the nucleus and the cytosol. Non-passive nucleocytoplasmic transport also requires nuclear transport receptors (NTR), which bind cargo molecules and shuttle them across the NPC. The NPC and NTRs constitute two fundamental layers of regulatory mechanisms that together determine the selective nuclear translocation of signal molecules and play essential roles in activating the precise response of a cell to environmental stimuli. Here we discuss recent findings in the NPC made by advanced structural biology approaches, and dissect distinct functions of different NPC components and NTRs in plants' responses to various biotic and abiotic stresses.

The nuclear pore complex: a strategic platform for regulating cell signaling

Contents Summary 25 I Introduction 25 II. Structural organization of the NPC 26 III. The role of NPCs in immune signaling 26 IV. The role of NPCs in hormone signaling 28 V. Conclusions 29 Acknowledgements 29 References 29 SUMMARY: Nuclear pore complexes (NPCs) are fundamental components of the eukaryotic cell. They perforate the nuclear envelope and serve as highly selective transport gates that enable bi-directional macromolecule exchange between the nucleus and cytoplasm. Recent studies illustrate that the NPC is not a static structural channel but a flexible environment and strategic player during nuclear signaling. The constitutional and conformational dynamics of the NPC allow it to tailor nucleocytoplasmic transport activities and define specific signaling output in response to various cellular and environmental cues. In this Insight, we review the roles of NPC constituents in immune activation and hormone signaling in plants, and discuss the possible role of the NPC as a legitimate platform for regulating cell signaling.

Reduced expression of AtNUP62 nucleoporin gene affects auxin response in Arabidopsis

BACKGROUND

The plant nuclear pore complex has strongly attracted the attention of the scientific community during the past few years, in particular because of its involvement in hormonal and pathogen/symbiotic signalling. In Arabidopsis thaliana, more than 30 nucleoporins have been identified, but only a few of them have been characterized. Among these, AtNUP160, AtNUP96, AtNUP58, and AtTPR have been reported to modulate auxin signalling, since corresponding mutants are suppressors of the auxin resistance conferred by the axr1 (auxin-resistant) mutation. The present work is focused on AtNUP62, which is essential for embryo and plant development. This protein is one of the three nucleoporins (with AtNUP54 and AtNUP58) of the central channel of the nuclear pore complex.

RESULTS

AtNUP62 promoter activity was detected in many organs, and particularly in the embryo sac, young germinating seedlings and at the adult stage in stipules of cauline leaves. The atnup62-1 mutant, harbouring a T-DNA insertion in intron 5, was identified as a knock-down mutant. It displayed developmental phenotypes that suggested defects in auxin transport or responsiveness. Atnup62 mutant plantlets were found to be hypersensitive to auxin, at the cotyledon and root levels. The phenotype of the AtNUP62-GFP overexpressing line further supported the existence of a link between AtNUP62 and auxin signalling. Furthermore, the atnup62 mutation led to an increase in the activity of the DR5 auxin-responsive promoter, and suppressed the auxin-resistant root growth and leaf serration phenotypes of the axr1 mutant.

CONCLUSION

AtNUP62 appears to be a major negative regulator of auxin signalling. Auxin hypersensitivity of the atnup62 mutant, reminding that of atnup58 (and not observed with other nucleoporin mutants), is in agreement with the reported interaction between AtNUP62 and AtNUP58 proteins, and suggests closely related functions. The effect of AtNUP62 on auxin signalling likely occurs in relation to scaffold proteins of the nuclear pore complex (AtNUP160, AtNUP96 and AtTPR).