Genome-wide Analysis And Functional Identification Of LBD Gene Family In Barley

Barley is recognized as one of the first crops domesticated for human consumption,and is also the fourth largest cereal crop over worldwide.Barley has been mainly used as food,feed,and for brewery and medicinal purposes.The Yangtze River basin is one of the major barley production zones in China.The frequent and rich rainfall in this area imposes stresses like waterlogging for barley,limiting greatly yield and grain quality.A large number of adventitious roots were sprout in the waterlogging-tolerant barley varieties in response to waterlogging stress.It has been reported that the LBD gene family plays an important role in regulating the development of plant lateral organs.In the present study,the barley LBD gene family was assayed at the whole genome level.A phylogenetic tree was constructed among barley,Arabidopsis,maize and rice,leading to screening and cloning of LBD gene associated with adventitious root development in barley.A transgenic study was conducted for verification of gene function.The present study would lay a foundation for the improvement of waterlogging-tolerant barley varieties and breeding for new barley varieties with molecular design approach.The main results are as follows:1.In the present study,24 HvLBD genes were identified across the whole barley genome.Based on the encoded protein structures,the HvLBD genes were classified into two classes,class Ⅰ(19 genes)and class Ⅱ(5 genes).Phylogenetic tree analysis showed that the HvLBD has high homology with OsARLl,ZmRTCL and ZmRTCS genes related to the regulation of adventitious root development.The Real-time PCR analysis revealed that the expression of HvLBD 19 in root node and adventitious roots was significantly higher than wild type under waterlogging.The transient gene expression analysis showed that the HvLBD 19 protein was localized in the nucleus.2.The full-length coding region of HvLBD19 gene was cloned,and the overexpression vector of HvLBD19 gene was constructed for Arabidopsis(Columbia).The transgenic plants were selected for functional verification.The results showed the SPAD value,plant height and dry weight of transgenic plants were significantly higher than wild type under waterlogging,indicating that overexpression of HvLBD19 enhanced the waterlogging tolerance of Arabidopsis.Expression of HvLBD19 gene was induced by application of exogenous hormone NAA.The growth of lateral root of transgenic HvLBD19 in Arabidopsis was regulated by exogenous hormone NAA.3.The overexpression vector of barley Golden Promise HvLBD19 gene was constructed.Positive transgenic lines of T2 generation were selected under waterlogging treatment.Under waterlogging stress,the SPAD value,root length,number of adventitious roots and antioxidant enzymes(SOD and POD)activity in transgenic lines were significantly higher than wild type.It was indicated that overexpression of HvLBD19 contributed to improvement of waterlogging tolerance of barley.