Study On The Function Of Photoregulatory Protein Kinases In Moso Bamboo

Moso Bamboo(Phyllostachys edulis)is a gramineous plant with ecological,economic and social values.It is an important forest resource in China.Meanwhile,some special events in bamboo growth and development(like rapid growth and flower-only-once)make it as valuable materials in basic plant research.Photoregulatory Protein Kinases(PPKs)are plant-specific tyrosine protein kinases which are involved in the regulation of osmotic stress,biological clock rhythm and photomorphogenesis in Arabidopsis.The name of this group of protein kinases is given based on their activities in catalizing the light-responsive phosphorylation of blue light photoreceptor CRY2 and several other light signaling proteins.The rapid growth of bamboo shares common features with the elongation of hypocotyl in Arabidopsis at cellular level,and PPKs play pivotal roles in promoting hypocotyl growth in Arabidopsis.Therefore,it is necessary to investigate the roles of PPKs in rapid growth of bamboo.However,the functions of PPKs have not been reported yet in bamboo.This study aims to isolate and characterize PPK genes from bamboo to pave the way for uncovering the role and molecular mechanism of PPKs in regulating bamboo rapid growth in future.In this study,the DNA and amino acid sequences of Arabidopsis PPKs(PPK1-4)were used as the query to search in Bamboo genomic database(BambooGDB)to identify the candidates of PPK genes in bamboo.Then the phylogenetic relationship of PPK proteins from different species was analyzed.Moreover,the mRNA expression of PPK genes in bamboo was profiled in different organs at different growth stages.The main results obtained in this study include:(1)10 homologous genes of PPK have been identified in bamboo genome,two genes from which were cloned(PH01001103G0290 and PH01000775G0130,referred as PhPPKa and PhPPKb,respectively).In addition,two homologous genes of CRY2 from bamboo(PH01000349G1020 and PH01000968G0540,referred as PhCRYa and PhCRYb,respectively)were cloned as well to used as potential substrates of PPKs for examing their biochemical activities;(2)The mRNA expression profling of PPK genes reveals that,the expression levels of PhPPKa and PhPPKb genes have no difference among various tissues at different growth stages,including roots of radicle,roots,young leaves,1 year leaves,5 and 8 year leaves.However,the expression level in leaves was significantly decreased during flowering.(3)The PhPPKa and PhPPKb genes were transformed into wild type Arabidopsis plants.The plants overexpressing either Arabidopsis PPK or bamboo PPK genes exhibited similar photomorphorgenic phenotypes,indicating that bamboo PPKs may play similar roles as Araboidopsis PPKs in Arabidopsis light signaling pathways;(4)PhPPKa could catalyze light-induced phosphorylation of both PhCRYa and PhCRYb in human cells;(5)PhPPKa/b could colocalize with PhCRYa/b in the nucleus.In summary,this study lays the basis for exploring the molecular mechanisms of rapid growth and light signaling transductions in bamboo plants.