Neofunctionalization leads to the acquisition of new function by one copy, whereas subfunctionalization renders the progenitor and the duplicated copy acquiring non-overlapping but complementary expression patterns.
Alternatively, one copy acquires a new function, or each copy adopts a portion of the functional role of the parental gene.
In other words, would the entire dosage compensation network have to be rebuilt from scratch each time any copy acquires a better mutation?
Subfunctionalization [ 6, 7], where an ancestral gene's functions are shared between the descendant genes, and neofunctionalization [ 5], where one copy acquires a novel gene function, are possible consequences of divergence following gene duplication.
Duplicated genes face three outcomes: non-functionalization (one copy becomes silenced); neo-functionalization (one copy acquires a novel, beneficial function, while the other copy retains the original function) or sub-functionalization (both copies become partially compromised by the accumulation of mutations) [ 35, 36, 21].
To test if the wXA21-like copies acquired novel interactors in wheat we have initiated the Y2H screening of wheat cDNA libraries.
Several experimental studies showed that duplicated Rab7 genes contributed to adaptation of plants to different environmental conditions and particular Rab7 copies acquired novel spatiotemporal roles and expression profiles.
During vertebrate evolution, genome of the common ancestor of vertebrates underwent two rounds of duplication events that led to increase in the copy number of several genes [ 67] and many of the extra copies acquired novel functions.
Lynch et al. [ 24] points out three possible outcomes of gene duplication: non-functionalization, in which one gene is silenced; neo-functionalization, where one of the copies acquires a new function; and sub-functionalization, in which case both copies become partially compromised [ 29- 31].
However, the relaxation of purifying selection (due to the initial redundancy) may allow some amount of divergence and occasionally can let one copy acquire a new function and be subsequently maintained by natural selection (neofunctionalization).
