Integrating Wheat Nucleolus Structure and Function: Variation in the Wheat Ribosomal RNA and Protein Genes

Abstract

We review the coordinated production and integration of the RNA (ribosomal RNA, rRNA) and protein (ribosomal protein, RP) components of wheat cytoplasmic ribosomes in response to changes in genetic constitution, biotic and abiotic stresses. The components examined are highly conserved and identified with reference to model systems such as human, Arabidopsis, and rice, but have sufficient levels of differences in their DNA and amino acid sequences to form fingerprints or gene haplotypes that provide new markers to associate with phenotype variation. Specifically, it is argued that populations of ribosomes within a cell can comprise distinct complements of rRNA and RPs to form units with unique functionalities. The unique functionalities of ribosome populations within a cell can become central in situations of stress where they may preferentially translate mRNAs coding for proteins better suited to contributing to survival of the cell. In model systems where this concept has been developed, the engagement of initiation factors and elongation factors to account for variation in the translation machinery of the cell in response to stresses provided the precedents. The polyploid nature of wheat adds extra variation at each step of the synthesis and assembly of the rRNAs and RPs which can, as a result, potentially enhance its response to changing environments and disease threats.

The Ribosomal DNA Loci of the Ancient Monocot Pistia stratiotes L. (Araceae) Contain Different Variants of the 35S and 5S Ribosomal RNA Gene Units

“…Our data on the intragenomic heterogeneity of the 35S rDNA in P. stratiotes, which we generated by sequencing one genomic clone and 10 random IGS fragments obtained by PCR, shed additional light on the genome organization and evolution of plant rDNA. Nucleotide alignment of the obtained sequences revealed significant variation in IGS size, primarily due to variation in the number of repeats upstream of the TIS, which is well documented to occur at inter species level (Chang et al, 2010;Huang et al, 2017;Hemleben et al, 2021), between cultivars (Polanco and De La Vega, 1997) or between different rDNA loci of the same genome (Sáez-Vásquez and Delseny, 2019; Appels et al, 2021). Apart from the variation in repeat numbers, the IGSs demonstrate considerable sequence homogeneity, with 95 SNPs among the 11 IGS sequences (∼3 SNPs per kbp) (Supplementary Figure 4).…”

“…Ribosomal DNA (rDNA) plays a pivotal role in organisms by producing the RNA components required to form ribosomes ( Moss and Stefanovsky, 2002 ; Appels et al, 2021 ; Hemleben et al, 2021 ). In plants, as in most eukaryotes, the rDNA encodes four ribosomal RNAs (rRNAs), which serve as the major structural and functional components of the ribosome.…”

Unlocking the genetic control of spring wheat kernel traits under normal and heavy metals stress conditions

“…Therefore, improving wax content helps in improving kernel yield and quality (Chaban et al 2021). Network 3 controlling the exportation of ribosomal subunit from nucleus, an important biological process that is essential in wheat growth, development, biotic response, and abiotic response (Kalinina et al 2018;Ramu et al 2020;Appels et al 2021). Therefore, this network is important in improving kernel yield and quality.…”

New insights on the evolution of nucleolar dominance in newly resynthesized hexaploid wheat Triticum zhukovskyi

“…As rRNA genes play a vital role in protein synthesis (Cockrell & Gerton, 2022), ND may have a significant impact on various aspects of biparental cell behavior, especially in interspecific hybrids and allopolyploids with ND (Jones & Baylin, 2002). ND associated with pairwise crossing among three ancestors of common wheat and per se has been well documented (Appels et al., 2021; Guo & Han, 2014). However, in the case of T. zhukovskyi , the dynamics of rDNA gene transcription and the accompanying dosage compensation of two A genomes are yet to be fully understood.…”