Given the higher complexity of plants, such as tobacco, compared to bacteria or yeast, variations in the expression levels of endogenous and reporter proteins from one cell to another can easily be imagined.
For prokaryotes and unicellular eukaryotes such as yeast, the variation in codon usage within a genome is thought to be due to natural selection acting to optimize protein production [ 5- 7].
In a recent large-scale study of beneficial mutations in the adaptation of yeast, background genetic variation was observed to be critical in determining the fate of new mutations (Lang et al. 2011).
Recent work within yeast suggests that variation in gene expression maps to promoter architecture and nucleosome occupancy (Tirosh and Barkai 2008b; Choi and Kim 2009; Tirosh, Barkai, et al. 2009; Tirosh et al. 2010).
This is also in line with previous observations in yeast, where H3K14ac variation was not systematically associated with differences in mRNA levels [ 6] and where ≥30% of QTLs of H3K14ac could not be attributed to genetic regulations of gene expression [ 15].
These motifs are not exact strings: while most binding sites for a given factor resemble a "consensus string" (for example, ACGCGT, the most common binding sequence for the MBP1 protein in budding yeast), mismatches and variations often occur.
Yeasts show remarkable variation in the organization of their mitochondrial genomes, yet there is little experimental data on organellar gene expression outside few model species.
Using this collection of 43 strains, we show that mutation rate varies at least 6-fold across the yeast genome, that this variation exists on a length scale of 50 100 kb, and that mutation rate is correlated with replication timing, potentially as a consequence of the temporal separation of two mechanisms of DNA damage tolerance: error-free DNA damage tolerance and translesion synthesis.
One of the first comprehensive studies on genetic variation of yeast strains, carried out using high-density oligonucleotide arrays containing up to 200,000 oligonucleotide probes from the yeast genomic sequence, unveiled differences at the level of single nucleotide polymorphisms and gene copy number alterations [ 29].
Capitalizing on natural variation in yeast strains and frequent meiotic recombination, She and Jarosz (2018) dissect and map to nucleotide resolution, simple and complex determinants of diverse phenotypic traits.
