THE ROLE OF ABSCISIC ACID AND COLD ADAPTATION IN IMPROVING THE CRYOPRESERVATION EFFICIENCY OF PYROPIA HAITANENSIS CONCHOCELIS

To explore whether abscisic acid (ABA) and cold adaptation can improve the cryopreservation efficiency of Porphyra sensu lato, the free living conchocelis of Pyropia haitanensis were treated with ABA (100 μmol/L) for 48h at 20℃, light intensity of 40 μmol·photons/(m²·s) with photoperiod 12L﹕12D or cultured in dark at 4℃ for 6 days before cryopreservation at –80℃. The effects of cryopreservation were evaluated by continuous measurement of algal survival rate after frozen, the maximum light quantum efficiency (F_v/F_m) of PSⅡ and the expression of cold adaptative related genes, such as P(H⁺)-ATPase, ald, Mn-sod A, Cu/Zn-sod 1, apx-2, hsp70-4, psy-2, gapdh, and gpxha-1. The results showed that: (1) Both ABA treatment and cold adaptation at 4℃ increased the survival rate of P. haitanensis conchocelis after cryopreservation, 59% in the ABA groups and 89% in the cold adapt groups; (2) The F_v/F_m of the conchocelis after cold adaptation recovered significantly faster than those of the other groups (P<0.05), with the optimal level after 35 day culture; (3) ABA treatment and 4℃ cold adaptation significantly up-regulated genes like P(H⁺)-ATPase, ald, Mn-sod A, Cu/Zn-sod 1, gapdh (P<0.01) and psy-2 (P<0.05) in the algae, but only ABA induced apx-2 and hsp70-4 (P<0.01). In summary, ABA treatment and cold adaptation can improve the frost resistance of P. haitanensis and improve the efficiency of cryopreservation. The cold adaptation method at 4℃ is simple and effective, and has greater application potential.