Cryopreservation Of The Excised Embryonic Axes From Davidia Involucrata And The Mechanism Of Dehydration Tolerance And Low Temperature Tolerance

Cryopreservation is at present considered to be the best way to preserve orthodox seeds.Davidia involucrata Baill.,native to China,is an endangered relict plant.Its seeds are both recalcitrant and dormant,so it is difficult to germinate and keep vigor for a long time under natural conditions.So,It is of great significance to realize a long-term preservation of the germplasm of D.involucrata.In the present study,the excised embryonic axes from Davidia involucrata were dehydrated rapidly in silica gel and subsequently thrown into liquid nitrogen for a cryopreservation,then the survival was evaluated by a tissue culture method.Meanwhile,the physiological mechanisms of dehydration tolerance and low temperature tolerance were also explored by conventional plant physiological experiments,such as relative conductivity measurement,antioxidant enzyme activity measurement,and proteomics and transcriptome techniques.The main results were as follows:(1)The excised embryonic axes from Davidia involucrata could tolerate dehydration to a certain extent,and the excised embryonic axes after a proper dehydration could successfully tolerate cryopreservation in liquid nitrogen.When dehydrated to 10.7 ± 0.2% moisture content,the survival rate was 55%,and after subsequent a cryopreservation in liquid nitrogen the survival rate could reach 35%.(2)The rapid dehydration in silica gel for 3 h and subsequent cryopreservation had no significant effect on lipid peroxidation of the excised embryonic axes.(3)The rapid dehydration in silica gel for 3 h did not result in significant leakage of electrolyte in the excised embryonic axes from D.involucrata,but subsequent cryopreservation greatly increased the leakage of electrolyte.(4)The activities of the several main antioxidant enzymes in the excised embryonic axes from D.involucrata had different response to rapid dehydration in silica gel for 3 h and subsequent cryopreservation.The rapid dehydration significantly increased the activity of CAT,but had no significant effect on the activities of SOD,APX and DHAR.While,compared with dehydration,cryopreservation significantly decreased the activity of SOD and significantly increased the activity of DHAR.(5)The mechanism of dehydration tolerance in excised embryonic axes from D.involucratamainly involved the synthesis,assembly,binding and metabolism of proteins and nucleic acids,and protein translation and posttranslational modification.(6)The mechanism of low temperature tolerance of dehydrated D.involucrata mainly concerned protein synthesis,molecular localization,energy metabolism and secondary metabolism.