Expression Of Gibberellin Related Genes And Cloning Of LdGAST1 During Dormancy Release Of Lilium Davidii Var.Unicolo By Low Temperature

Lilium davidii var.unicolor have a sweet taste,little fibre and no bitterness,making them the finest of lilies.To ensure good merchantability of the seed bulbs and annual production,it is essential to maintain the dormant state of the bulbs and to break dormancy early.The long developmental and dormant period of the lily of Lanzhou makes it an excellent material for research on dormancy.At present,the most important means of relieving dormancy in lily seed bulbs is still low-temperature treatment,and the low-temperature cold requirements of lily seed bulbs vary considerably between species,sizes and origins.However,the molecular mechanism of dormancy in lily bulbs needs to be further investigated.In order to explore the mechanism of endogenous hormone changes in the dynamic physiological activities of lily bulb dormancy release,this study was conducted to identify the key GAs genes involved in the release of bulb dormancy and their expression characteristics,and successfully cloned the gibberellin-stimulated response protein LdGAST1,and carried out biological information analysis and subcellular localization analysis.The results of this study are as follows.The main findings of this paper are as follows.1.Lilium davidii var.unicolor bulbs stored at 4℃for 100 days could completely release dormancy,and the terminal buds grew normally and the germination rate reached 100%after planting;.Measurements of endogenous hormone content showed that during the process of bulb dormancy release,the contents of GA,IAA and MEJA increased and the contents of ABA,JA,SA and MESA decreased,with the most significant changes in the contents of GAs.Compared with the deep dormancy period,the contents of GA₁and GA₃did not change significantly during 100 d of low temperature storage,while the contents of GA₄and GA₇increased significantly,among which,GA₄was the highest.Therefore,it was tentatively determined that GA₄and GA₇were the main GA functions in the process of dormancy release in Lilium davidii var.unicolor.After using 100mg/L GA₄to soak lily bulbs and then continuing to store them at low temperature for 0d,50d and 100d,the bulbs released dormancy 18d,20d and 3d earlier respectively.Meanwhile,the terminal bud germination rate of the bulbs in the0d and 50d groups also increased by This indicated that GA₄could partially replace the low temperature treatment2.qRT-PCR was used to determine the expression of seven genes with key roles in the biosynthetic pathway of GAs.The results showed that the expression of GAST1 showed the most significant trend,with 2.5-fold up-regulated expression;during the dormancy release period,the key genes regulated by low temperature were GAST1,GA20ox and GA3ox,among which GA20ox showed a special trend,with its expression down-regulated under exogenous GA treatment,in contrast to GA3ox and GA2ox.Based on the expression analysis,we tentatively concluded that GA20ox could regulate the balance of endogenous GA content by suppressing its own expression,thus regulating the dormancy of lily seed bulbs.3.The complete CDS sequence of LdGAST1 was successfully cloned.The gene is predicted to encode a hydrophilic protein that does not possess a natural coiled helix and is highly conserved at the C-terminus.In addition,the subcellular localization identified the protein encoded by LdGAST1 as a cytosolic protein,and it is highly likely to be expressed on chloroplasts at the same time,which provides a direction for investigating its function.