Abstract:
Hox gene clusters play an important role in the early embryonic development, tissue differentiation and morphogenesis in animals.
Megalobrama amblycephala, also
known as Wuchang fish, is an economically important freshwater fish and widely distributed in lakes in the middle and lower reaches of the Yangtze River in China.In order to explore the
Hox distribution, evolution and expression patterns in
M. amblycephala, we conducted a series of analyses based on the whole genome
M. amblycephala. In the present study, we identified all the
Hox clusters of
M. amblycephala from the whole genome data. Combined with the multiple methods, we analyzed chromosome distribution and constructed the
Hox phylogenetic tree based on protein sequences. In addition, the expression patterns of
Hox in different tissues were further investigated by calculating the number of transcriptional fragments (FPKM).The results showed that 49
Hox genes were identified in the genome of
M. amblycephla, and were divided into 7 groups:
HoxAa,
HoxAb,
HoxBa,
HoxBb,
HoxCa,
HoxCb and
HoxDa. Transcriptome results indicated that
M. amblycephala Hox gene family had different expression patterns. There were significant differences in the expression level of all
Hox genes in the muscle of
M. amblycephala and
Danio rerio, while the expression pattern was similar. In the
HoxA cluster,
HoxA10
b, HoxA3
a,
HoxA2
a and
HoxA1
a were highly expressed in the muscles of
M. amblycephala, and the expression level was higher than that of
D. rerio;
HoxA13
a and
HoxA13
b are not expressed in the muscle of both of fishes; In the
HoxB cluster,
HoxB10
a,
HoxB9
a and
HoxB7
a were highly expressed in muscle tissue of
M. amblycephala, while
HoxB9
a,
HoxB8
a,
HoxB7
a and
HoxB6
a were highly expressed in muscle tissue of
D. rerio. In the
HoxC cluster,
HoxC9
a,
HoxC2
a,
HoxC3
a and
HoxC6
b are highly expressed in muscle tissue of
M. amblycephala and
HoxC8
a and
HoxC3
a are highly expressed in
D. rerio, while
HoxC13
a,
HoxC12
a,
HoxC11
a,
HoxC4
a,
HoxC1
a,
HoxC13
b,
HoxC12
b and
HoxC11
b are very low or even not expressed in muscle tissue of the two fish species; In the
HoxD cluster,
HoxD10
a,
HoxD9
a and HoxD3
a are highly expressed in muscle tissue of
M. amblycephala and
HoxD9
a is highly expressed in
D. rerio, while the expression levels of
HoxD13
a,
HoxD12
a and
HoxD11
a are not expressed in muscle tissue of
M. amblycephala and
HoxD13
a is not expressed in muscle tissue of
D. rerio. In addition, comparative transcriptome analysis of three embryonic stages and three tissues of
M. amblycephala indicated that
HoxA2
a,
HoxA3
a,
HoxB9
a,
HoxB3
a,
HoxB8
a,
HoxB1
b,
HoxB5
a,
HoxB5
b,
HoxC3
a and
HoxC4
a were highly expressed at the juvenile fish, while others showed low or even no expression in muscle, intermuscular bone and connective tissues except
HoxB7
a,
HoxB10
a and
HoxB9
a,
HoxC3
a and
HoxC8
a. In the
HoxD family,
HoxD9
a,
HoxD10
a and
HoxD11
a were expressed in the stage II of embryo. Taken together, these results may lay the foundation for further exploring the function of the
Hox gene family of
M. amblycephala, and may also provide reference data for other fish
Hox studies. In addition, studying the expression patterns of
Hox in the formation of intermuscular bone of
M. amblycephala also provides reference and theoretical basis for the study of intermuscular bone in other bony fishes.