3.1. Identification and classification of Hsf genes in the citrus genome
CDS sequences corresponding to putative Hsf genes from citrus
(CcHsfs) were searched in the C. clementina genome database, and 29
genes encoding putative CcHsf proteins were identified. All candidate
CcHsf proteins were surveyed, and incomplete sequences were
removed. This resulted in the selection of 18 complete sequences.
These CcHsf genes were distributed on seven of the nine putative citrus
chromosomes, excluding chromosomes 4 and 8, with the largest
number, comprised of five CcHsf genes, located on chromosome 2. The
molecular weight of the deduced proteins varied from 24.08 to
56.29 kDa (Table 2).
To investigate the evolution of CcHsfs, an unrooted phylogenetic tree
was generated by using the 18 C. clementina Hsfs, 23 Solanum
lycopersicum Hsfs (SIHsfs) and 21 Arabidopsis thaliana Hsfs (ATHsfs)
(Fig. 1). These Hsf members were clearly grouped into three different
clades corresponding to the main Hsf classes A, B and C. Within the
A-type clade, nine distinct sub-clades were resolved, all of which
comprised the citrus Hsf sequences. Five sub-clades were resolved
within the B-type clade, each sub-clade containing at least one citrus
Hsf sequence. The C-type Hsfs from the three plant species also