Abstract
Citrus
, as one of the globally important fruit trees, has been an object of interest for understanding genetics and evolutionary process in fruit crops. Meta-analyses of 19
Citrus
species, including 4 globally and economically important
Citrus sinensis
,
Citrus clementina
,
Citrus reticulata
, and 1
Citrus
relative
Poncirus trifoliata
, were performed. We observed that codons ending with A- or T- at the wobble position were preferred in contrast to C- or G- ending codons, indicating a close association with AT richness of
Citrus
species and
P. trifoliata
. The present study postulates a large repertoire of a set of optimal codons for the
Citrus
genus and
P. trifoliata
and demonstrates that GCT and GGT are evolutionary conserved optimal codons. Our observation suggested that mutational bias is the dominating force in shaping the codon usage bias (CUB) in
Citrus
and
P. trifoliata
. Correspondence analysis (COA) revealed that the principal axis [axis 1; COA/relative synonymous codon usage (RSCU)] contributes only a minor portion (∼10.96%) of the recorded variance. In all analysed species, except
P. trifoliata
, Gravy and aromaticity played minor roles in resolving CUB. Compositional constraints were found to be strongly associated with the amino acid signatures in
Citrus
species and
P. trifoliata
. Our present analysis postulates compositional constraints in
Citrus
species and
P. trifoliata
and plausible role of the stress with GC
3
and coevolution pattern of amino acid.