TABLE 1.

Examples of cellular and functional diversification of protein isoforms in response to environmental stresses.

Factors determining protein isoforms	References
Transcriptome reprogramming under cold: histone H2AZ instead of canonical H2A isoform → altered pattern of euchromatin vs. heterochromatin	Kumar and Wigge, 2010
Cellular localization—different cofactor:
SOD isoforms: Cu/Zn-SOD—cytoplasmic; Mn-SOD—mitochondrial;	Kosová et al., 2018
Fe-SOD—chloroplast
Cellular localization—different function: cytoplasmic (C) vs. nuclear (N) protein isoforms
eIF3: translation regulation (C) × cell cycle regulation (N)	Thompson et al., 2004
enolase: glycolytic enzyme (C) × transcriptional regulator (N	Lee et al., 2002
Fine tuning of biological processes—isoforms with overlapping functions:
Peroxiredoxin and thioredoxin isoforms—better regulation of redox stress in photosynthetic electron transport chain (ETC)
Enhanced CBF gene copy number in winter vs. spring barley genotype → enhanced low-temperature (LT) tolerance in winter-type plants	Knox et al., 2010
Different expression patterns and interacting partners: Hsc70-1, Hsc70-3—constitutive; Hsc70-2—pathogen-inducible, interacting with SGT1 involved in R-gene mediated resistance	Noël et al., 2007