Physiological And Biochemical Responses Of Gerbera Cultivars To Heat Stress And Anscriptome Analysis

Gerbera(Gerbera jamesonii Bolus)is one of the most important cut flowers in the world.It has broad markets and a wide range of applications.However,although gerbera can product annualy,the growth of young gerbera plants always slows down and the plants even die when suffering the high temperature in summer,causing the decreasedyield of the cut flower production.In this study,six varieties of Gerbera jamesonii seedlings including ‘Meihongheixin',‘Beijixing',‘Shijihong',‘Linglong',‘Dadifen' and ‘Taiyangfengbao' were used as materials.The morphological,physiological and biochemical responses of the six varieties to heat stress were investigated.And the molecular mechanism of heat-resistant cultivar ‘Meihongheixin' was studied by the transcriptome sequencing.The research preliminarily reveals the physiological and molecular mechanisms of the gerbera to heat stress,lays the foundation for heat-resistance breeding and further study of molecular mechanisms,and also provides a theoretical basis to the heat resistance reseach of ornamental plants.Our major results were as follows:1.The six gerbera cultivars were exposed to heat stress by different temperature and treated time.And we found that the electrolyte leakage of all tested cultiveas were increased in different degreed when the level of heat stress rised.Meanwhile,results showed that 1 d-treatment of 45°C was the optimal condition to distinguish the heat tolerance among different gerbera cultivars.2.The heat stress resulted in increased proline and malondialdehyde(MDA),and decreased soluble protein and chlorophyll content of gerbera cultivars in different degrees,which were consistant with the phenotypes of gerbera cultivars under heat stress.Our results demonstrated that among the six gerbera cultivars,‘Meihongheixin' is a heat-resistant cultivar,whereas ‘Beijixing' is a heat-sensitive one.‘Shijihong' and ‘Linglong' are relatively heat-resistant cultivars,and ‘Dadifen' and ‘Taiyangfengbao'are relatively heat sensitive.3.The heat-resistant cultivar ‘Meihongheixin' was treated by heat stress and 0 h-,1 h-,and 6h-treated samples were analyzed respectively by the technology of transcriptome sequencing.We obtained 141 007 unigenes of gerbera with expression changing significantly under heat stress.GO classificationanalysis showed that most unigenes were associated with thecellular process,metabolic process and binding function.KOG classification analysis indicated that most unigenes were associated with the general function prediction only,protein turnover and signal transduction mechanisms.KEGG pathway analysis found that most unigenes might have function of metabolism.Among them,the enriched pathways in all heat-treated pointsincluded the processs of endoplasmic reticulum protein processing,spliceosome,MAPK signaling pathway and so on.4.Most differentially expressed genes of the greberas were significantly up-regulated by heat stress when compared with controls.Among them,expression of heat shock proteins(HSPs)family changed most significantly,suggesting that HSPs might play an important role in the resistance to heat stress in gerbera.