Methods: In the present study, displacement loop (D-loop) sequences were used to evaluate the genetic relationship and diversity of seven tilapia populations that are widely cultured in China; this was done specifically to speculate on the maternal ancestry of red tilapia strains. Three red tilapia varieties of Oreochromis ssp., Taiwan (TW), Israel (IL), and Malaysia (MY) strains and other populations, including O. aureus (AR), O. niloticus (NL), O. mossambicus (MS), and the GIFT strain of O. niloticus, were collected and analyzed in this study.
Results: A total of 146 polymorphic sites and 32 haplotypes of D-loop sequences were detected among 332 fish and four major haplotypes were shared among the populations. The TW and NL populations had a greater number of haplotypes (20 and 8, respectively). The haplotype diversity (Hd) and nucleotide diversity (π) of each population ranged from 0.234 to 0.826, and 0 to 0.060, respectively. The significant positive Tajima's D value of neutral test were detected in the NL, IL, and MY populations (P 0.05). The nearest K2P genetic distance (D = 0.014) was detected between the MS and TW populations, whereas, the farthest (D = 0.101) was found between the GIFT and AR populations. The results from the molecular variance analysis (AMOVA) showed that there was an extremely significant genetic variation observed among the populations (P
RESULTS: In this study, 1316 TFs belonging to 52 families were identified from the transcriptomic data, and corresponding expression profiles during the L. japonica flower development were comprehensively analyzed. 917 (69.68%) TFs were differentially expressed. TFs in bHLH, ERF, MYB, bZIP, and NAC families exhibited obviously altered expression during flower growth. Based on the analysis of differentially expressed TFs (DETFs), TFs in MYB, WRKY, NAC and LSD families that involved in phenylpropanoids biosynthesis, senescence processes and antioxidant activity were detected. The expression of MYB114 exhibited a positive correlation with the contents of luteoloside; Positive correlation was observed among the expression of MYC12, chalcone synthase (CHS) and flavonol synthase (FLS), while negative correlation was observed between the expression of MYB44 and the synthases; The expression of LSD1 was highly correlated with the expression of SOD and the total antioxidant capacity, while the expression of LOL1 and LOL2 exhibited a negative correlation with them; Many TFs in NAC and WRKY families may be potentially involved in the senescence process regulated by hormones and reactive oxygen species (ROS). The expression of NAC19, NAC29, and NAC53 exhibited a positive correlation with the contents of ABA and H2O2, while the expression of WRKY53, WRKY54, and WRKY70 exhibited a negative correlation with the contents of JA, SA and ABA.
CONCLUSIONS: Our study provided a comprehensive characterization of the expression profiles of TFs during the developmental stages of L. japonica. In addition, we detected the key TFs that may play significant roles in controlling active components biosynthesis, antioxidant activity and flower senescence in L. japonica, thereby providing valuable insights into the molecular networks underlying L. japonica flower development.