Functional Analysis Of DELLA Genes Related To Dormancy In Prunus Mume

Mei (Prunus mume Sieb. et Zucc.) is an ornamental flower and fruit tree in Rosaceae, which has been domesticated for more than 3000 years in China. Compared with other Prunus species, mei’s flowers can bloom in early spring in south of the Yangtze river region. Prunus trees need accumulate enough chilling before their bud burst and blooming.Previous studies showed that gibberellin improved bud burst in the rest period in many woody plants, but it was less reported about the effection of gibberellin in bud burst in mei during dormancy stage. The molecular mechanism of gibberellin improving seed germination was clarified clearly, however, less was reported about the molecular mechanism of gibberllin and bud dormancy releasing. The key regulator, DELLA, in gibberellin signaling pathway, was reported had connection with many growth and development stages in plants, but never reported its function in bud dormancy releasing inTo study the effection of gibberellin on dormancy bud burst in mei and to explore the molecular mechanism of bud dormanacy releaseing regulated by gibberellin and to clarify the functions on DELLA in the rest period in mei, the paper invesgated the changes of different hormenes of buds in rest period and the effects of gibberellin in bud release, genome wide anlysis of GRAS gene family and cloned and functional analysed DELLA genes in GRAS gene family. The main points were below.1. Mei cultivars’Changsilve’and’Fenhongzhusha’ was calculated to 241 h of chilling requirement to release bud dormancy and’Mingxiaofenghou’ was calculated to 579 h according to 0-7.2 ℃ model. The analysis of hormone changes in different cultivars showed that the content of GA3 of 3 cultivars increased before bud release. The results of hormenes ratio showed that gibberelline probally balance out the effects of ABA and improve bud release.2. Mei cultivars’Fenhongzhusha’ and ’Mingxiaofenghou’ was used to analysis effects of GA3 in bud release. The results showed that compared with contral, the bud release rate of spraying 50 mg/L GA3 and 100 mg/LGA3 on’Fenhongzhusha’ increase 25% and 32%. Treats of spraying 50 mg/L GA3 on ’Mingxiaofenghou’ improve bud release of ’Mingxiaofenghou’ 35 d earlier than natural timing.3. Genome wide analysis of GRAS gene family identified 46 genes. The envolution of GRAS gene family and main functions of theses genes in root, stem, leaf, flower development and fruit development were clarified.2 DELLA genes in mei which probably connected with GA signaling path way were predicted.46 genes were analysised by physicochemical property, gene structures, phylogenetic analysis, chromosome location analysis and expression analysis. The physicochemical analysis showed that all 46 genes were hydrophilic and 84% genes had no introns. Out of 46 identified GRAS genes,45 were located on the eight P. mume chromosomes. Phylogenetic analysis showed that these genes could be classified into 11 groups. Group X was P. mume-specific, and three genes of Group IX were speculate that they existe before the divergence of dicotyledons and monocotyledons.11 genes showed high expression levels in roots,4 in stems and 6 in leaves.4. PmDELLA1 and PmDELLA2 were colned and functionally analysised. Expression analysis showed that 2 PmDELLAs were both down-regulated in dormancy releasing in high chilling requirement cultivars. And they had different function in dormancy releasing in low chilling requirement cultivars. Transgenic lines showed GA deficiency phenotype and reduced the response to exogenous GA3. Over-expressing PmDELLAl and PmDELLA2 showed shorter in plant height, smaller in rosette diameter, and decrease in bloomed ratio and the difference values of control on GA3 media and that on normal media and the difference values of transgenic lines of PmDELLAs on GA3 media and that on normal media had significant difference. It was confirmed that the two PmDELLAs were partially conserved with genes encoding DELLA proteins in arabidopsis, regulating gibberellin signaling in mei and further connecting with bud release of mei.The paper revealed the effects of gibberellin in bud release and conformed two PmDELLAs were partially conserved with genes encoding DELLA proteins in arabidopsis, regulating gibberellin signaling in mei and further connecting with bud release of mei. These anlysiss not only offered valuble information in mei bud release molecular mechanism but also other woody species in Rosaceae.