Abstract
BackgroundBoth Gossypium hirsutum and G. barbadense probably originated from a common ancestor, but they have very different agronomic and fiber quality characters. Here we selected 17 fiber development-related genes to study their structures, tree topologies, chromosomal location and expression patterns to better understand the interspecific divergence of fiber development genes in the two cultivated tetraploid species.ResultsThe sequence and structure of 70.59% genes were conserved with the same exon length and numbers in different species, while 29.41% genes showed diversity. There were 15 genes showing independent evolution between the A- and D-subgenomes after polyploid formation, while two evolved via different degrees of colonization. Chromosomal location showed that 22 duplicate genes were located in which at least one fiber quality QTL was detected. The molecular evolutionary rates suggested that the D-subgenome of the allotetraploid underwent rapid evolutionary differentiation, and selection had acted at the tetraploid level. Expression profiles at fiber initiation and early elongation showed that the transcripts levels of most genes were higher in Hai7124 than in TM-1. During the primary-secondary transition period, expression of most genes peaked earlier in TM-1 than in Hai7124. Homeolog expression profile showed that A-subgenome, or the combination of A- and D-subgenomes, played critical roles in fiber quality divergence of G. hirsutum and G. barbadense. However, the expression of D-subgenome alone also played an important role.ConclusionIntegrating analysis of the structure and expression to fiber development genes, suggests selective breeding for certain desirable fiber qualities played an important role in divergence of G. hirsutum and G. barbadense.
Highlights
Both Gossypium hirsutum and G. barbadense probably originated from a common ancestor, but they have very different agronomic and fiber quality characters
There was a single copy of Exp1 in the diploid species and two distinct copies in TM-1, the Exp1 sequence from Hai7124 was of only one type, though more than 10 clones were selected randomly to sequence
The sequence from Hai7124 has a closer relationship with G. raimondii than with G. herbaceum
Summary
Both Gossypium hirsutum and G. barbadense probably originated from a common ancestor, but they have very different agronomic and fiber quality characters. Humans have independently domesticated four different species for their fiber, two of which are diploids, Gossypium herbaceum and G. arboreum, and two are allopolyploids, G. hirsutum and G. barbadense [1]. Alhough G. hirsutum and G. barbadense probably originated from a single hybridization event between. The high yield potential and diverse environmental and production system adaptability of G. hirsutum make it the most widely cultivated species, accounting for about 97% of the world’s cotton fiber [2]. Despite its higher fiber quality, the narrow adaptation range and low yield of G. barbadense limit its cultivation. The introgression of favorable alleles from G. barbadense to G. hirsutum would likely improve the fiber quality of
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