Luciobarbus Capito Gonadal Development, Sex Hormone And Its Receptor Gene Expression Analysis

Luciobarbus capito has high economic value with fresh meat, fast growth, strong resistance. At present, China’s freshwater resource-poor, low utilization of saline alkali water, Luciobarbus capito as good saline water aquaculture species, study it has important significance. However, the current farming persists reserve its first sexual maturation time is unclear, induce labor to grasp inaccurate, molecular biology aspects of gonad development is still in a blank state of some problems. The situation of seedling production less has seriously hampered the Luciobarbus capito promotion. Therefore, the study use of histology, endocrinology and molecular biology research methods to study the change of body length, body weight, sex hormone levels, changes of gonadal tissue and the expression of hormone receptors in the process of gonad development.Results and conclusions are as follows:1.Body length and body weight increased significantly with age.Age one’s body length increment per year(16.61) is greter than the amount of increase of 2 to 5 age. Age five’s body weight increment per year(874.81g) is greter than the amount of increase of 1 to 4 age. The body length-weight relationship was W = 0.012L2.99(R2 = 0.99), and power exponent is 3, whic h belonged to the type of smooth growth. It also can be described by the Von Bertalanffy growth equation Lt=107.43[1-e-0.15(t +0.067)] and Wt=12939[1-e-0.15(t+0.067)]2.99.2.Serum sex steroid levels were changed with age. In male, the levels of serum testosterone(T) reached the highest value 1.12±0.81ng/ml at age 5 and the levels of serum 17β-estradiol(E2) were lower than female. In female, levels of E2 were rising from age 1 to age 4 and reached the highest level(713.00±424.89pg/ml) at age 4. There was no significant difference between age 1-5 in serum T levels. Age five’s gender can be determined by the ratio of 17β-E2/T.3.The spermary has typical lobular structures, and between the seminiferous lobule, there is leydigs cells, where have sertolis cell and spermatangium in it. Sperms developed can be divided into five stages, including androgene, first spermatocyte, secondary spermatocyte, spermatoblast and mature sperms. Male’s gonado somatic index(GSI) reached the peak value at the stage Ⅴ. Under artificial conditions, female spawn once a year and its oocyte development is asynchronous. The gonado somatic index of ovary was between 0.51%- 8.9%, and reached the peak value 8.9% at stage Ⅴ. The minimum age of sexual maturity is 4 years old in male and 5 years old in female.4.The androgene receptor gene length coloned from Luciobarbus capito is 3045 bp, only one subtype. Its open reading frame length is 2550 bp. The deduced protein is composed of 849 amino acids, with an estimated molecular weight of 93.8 kDa. Aligned with known full- length AR amino acid sequences using Blastp, highest identity Luciobarbus capito and Spinibarbus denticulatus for 84%. Real-time PCR show : AR gene is expressed in gonads, brain, liver, kidney and all tissues exmined. The results revealed that AR play a important role in the development of gonad.5.There have four estrogene receptor gene subtubes in Luciobarbus capito. The estrogene receptor gene α1 coloned from Luciobarbus capito is 2016 bp. Its open reading frame length is 1689 bp. The deduced protein is composed of 562 amino acids, with an estimated molecular weight of 62.4 k Da. Aligned with known full- length ERα amino acid sequences using Blastp, highest identity Luciobarbus capito and Spinibarbus denticulatus for 94%. The estrogene receptor gene β1 coloned from Luciobarbus capito is 1806 bp. Its open reading frame length is 1707 bp. The deduced protein is composed of 568 amino acids, with an estimated molecular weight of 63.3 kDa. Aligned with known full- length ER amino acid sequences using Blastp, highest identity Luciobarbus capito and Onychostoma barbatulum for 94%. The estrogene receptor gene β2 coloned from Luciobarbus capito is 2006 bp. Its open reading frame length is 1839 bp. The deduced protein is composed of 612 amino acids, with an estimated molecular weight of 67.8 k Da. Aligned with known full- length ER amino acid sequences using Blastp, highest identity Luciobarbus capito and Onychostoma barbatulum for 95%. Real-time PCR show : ERβ gene is expressed in gonads, brain, liver, kidney and all tissues exmined. The highest expression of ERβ1 in female ovaries, and highest expression of ERβ2 in female liver. Speculated that the ERβ2 was associated with the liver production of the yolk protein.