Objective To study the function of ThP5CS and Thδ-OAT in T. hybrid 'Zhongshanshan 407' (Taxodium mucronatum ♀×T. distichum ♂), and to explore the relationships between the genes and drought resistance of T. hybrid 'Zhongshanshan 407'. This research would provide candidate gene resources for resistance breeding in Taxodium.

Method Rapid-amplification of cDNA ends (RACE) was applied to clone the full-length complementary DNA (cDNA) sequences of P5CS and δ-OAT in T. hybrid 'Zhongshanshan 407'. And then, the structures and functions were predicted with bioinformatics analysis. Finally, a natural drought and rewatering experiment was conducted to investigate the expression patterns of ThP5CS and Thδ-OAT by semi-quantitative RT-PCR (sRT-PCR) and quantitative real-time PCR (qRT-PCR).

Result The cDNA sequences of P5CS and δ-OAT in T. hybrid 'Zhongshanshan 407' were isolated and then were named as ThP5CS and Thδ-OAT. The full-length sequence of Thδ-OAT and ThP5CS contained open reading frames (ORF) of 1 494 bp and 1 545 bp respectively, and encoded polypeptides of 497 and 514 amino acids residues. The protein sequences of Thδ-OAT exhibited 92% sequence identities with Pinus sylvestris L., and the protein sequences of ThP5CS exhibited 87% sequence identities with Anthurium amnicola. sRT-PCR and qRT-PCR analysis showed that in T. hybrid 'Zhongshanshan 407' and its parents, ThP5CS showed an increasing expression pattern and then decreasing in the period of drought and recovery. While the relative expression of Thδ-OAT showed differentiations in T. hybrid 'Zhongshanshan 407', T. distichum, and T. mucronatum.

Conclusion ThP5CS might be important in response of Taxodium to drought and could play a leading role in proline synthesis.