Regulation Of CBF Signaling Pathway On Plant Growth At Low Temperature And Its Breeding Application

The growth area and yield of crops largely depend on temperature. Low temperature is one of the major environmental factors limiting plant growth and development. The regulatory network of crosstalk between cold reponse and growth in plants and transgenic engineering in plant breeding for cold tolerant crops have been priorities in current plant research.The C-repeat binding factor (CBF) signaling pathway has been identified as playing a key role in cold response of higher plants. This work characterizes functions of downstream gene CbCOR15a as well as upstream genes CbICE53and CbCBF involed in CBF signaling pathway from cold tolerant species Shepherd’s purse(Capsella bursa-pastoris) to estimate the perspective of application of these genes in molecular breeding.The results reveal that CbCOR15α and CbICE53confer significantly enhanced cold tolerance in cold sensitive species tobacco without obvious growth repression, and can be considered as potential candidates for engineering of cold tolerant crop breeding. CbCBF transgenic tobacco plants exhibit enhanced chilling and freezing tolerance as well as obvious growth retardation. Thus the elimination of growth repression cause by C8F-like genes is crucial for utilization of CBFs in plant breeding.For the goal of producing transgenic plants using CbCBF with stronger cold tolerance but without growth retardation, further investigation in the mechanism involved in the regulation by CBFs in plant growth is necessary. This work analyzes the crosstalk between CBF1/2/3and gibbrellins as well as DELLA proteins using the model plant Arabidopsis thaliana. The growth retardation caused by CBF1/2/3overexpression can be restored by exogenous GA3treatment. In CBF1/2/3transgenic plants, the contents of bioactive gibbrellins are obviously reduced and DELLA proteins are accumulated. Moreover, the DELLA gene RGL3is activated by CBF1/2/3, and the GA2ox7gene participating in deactivation of bioactive gibbrellins is the direct target of CBF3. RNA-seq data reveals that CBF1/2/3affect ABA and jasmonic signaling in addition to GA, and significantly downregulate the genes involved in apoptosis. These demonstrate that CBFs regulate plant growth through interplay with phytohormones and apoptosis signaling.In summary, the present work provides cold responsive genes involved in CBF signaling pathway from Capsella bursa-pastoris and suggests strategies for co-transgenic engineering in cold tolerant crop breeding. Likewise, the investigation of regulation by CBFs in plant growth will contribute to the application of CBF genes in molecular breeding.