Molecular Cloning Of ZmPP6C Gene And Its Expression In Response To Light And Stress Treatments In Maize(Zea Mays L.)

PP6C is the catalytic subunits of Ser/Thr protein phosphatase 6(PP6)gene,which plays important roles in auxin transport polarity,ABA(abscisic acid)signal transduction,flowering time control though light signaling pathway.To clarify structural characteristics of PP6 C protein and the evolution relationships among plant PP6 C homologs,we cloned ZmPP6 C gene by RT-PCR,and analysised the expression patterns of ZmPP6 C genes in response to different light qualities,dark to different light transitions,long-day or short-day treatments,and abiotic stresses.The results showed that:1.The amino acid sequence of the Ser/Thr protein phosphatase subunits are highly conserved in evolution.Sequence analysis showed that the open reading frame(ORF)of ZmPP6 C possesses 912 nucleotides and encodes 303 amino acid residues with one PP2 Ac domain(the catalytic subunits of Ser/Thr protein phosphatase 2A).Phylogenetic analysis indicated that ZmPP6 C belonged to the same branch with the PP6 C of Sorghum bicolor,and showed high similarity to all PP6 C proteins from other monocotyledons and dicotyledons.The percentage of amino acid sequence between monocotyledons and dicotyledons was about 91%,however ZmPP6 C and Sb PP6 C was 99.67%.2.Further quantitative RT-PCR(qRT-PCR)assays indicated that ZmPP6 C was highly expressed in leaves;and low level expression was detected in stems,stamens,pulvinuses,sheaths,and pistils.Transcription level of Zmpp6 c in leaves was 7.9 times higher than that in roots.ZmPP6 C transcription could respond to different light quality and dark to deffirent light transitions,especially transitions from the dark to far-red or red light conditions.During dark-to-red transition,transcription abundance of ZmPP6 C reached a peak after B73 seedlings were transferred to far-red light for 30 minutes,then declined rapidly to a relative low level and kept it until 24 h.During dark-to-far-red transition,transcription level of ZmPP6 C reached a peak after the seedlings were transferred to red light for 15 minutes,then declined rapidly;then it began to increased slowly 1 h later and reached a new peak with 7.2 times higher than that in the dark after seedlings were transferred to red light for 24 h.3.Transcription abundances of ZmPP6 C could respond to circadian treatments(both long-day and short-day conditions).It suggested that ZmPP6 C might be involved in flowering time control through light signaling pathway.Transcription abundances of ZmPP6 C had a peak both in the light phase and in the dark phase of during the long-day treatment.The first peak took after light exposure for 10 h and the second peak happened at 5 h after entering darkness.The expression of ZmPP6 C was ups and downs during the short-day treatment.The highest peak took at 10 h after entering darkness,and the subpeak happened after light exposure for 8 h.4.Transcription abundances of ZmPP6 C were down-regulated at the early stage and up-regulated in later stage during abiotic stress treatments such as high osmosis,high salt and water logging.Transcription abundances of ZmPP6 C after 200 m M NaCl treatment for 12 h,24 h,and 48 h were 0.8,1.1,and 2.6 times as that of the mock treatment,respectively.After 20% of PEG6000 treatment for 48 h,transcription abundances of ZmPP6 C reached approximately 4.5 times as that of the mock treatment.After seedlings were treatment with water logging for 5 d and 7 d,transcription abundances of ZmPP6 C were 1.3 and 4.1 times higher than that of the mock treatment.When seedlings were transferred back to normal green house condition for 3 d and 7 d,transcription abundances of ZmPP6 C reached 3.0 and 6.9times as that of the mock treatment.Thus,ZmPP6 C might be involved in abiotic stress response in maize.