Manipulating the circadian clock to increase gene expression

Abstract

A method of increasing gene expression by manipulating the circadian clock is described that includes transforming a photosynthetic organism to include an expression control sequence that modulates the expression of a clock gene to increase expression of a target gene. Photosynthetic organism having a modified circadian cycle reflecting this method are also described.

1 . A method of increasing gene expression by manipulating the circadian clock, comprising transforming a photosynthetic organism with (a) a first promoter and a clock gene, wherein the first promoter results in overexpression of the clock gene to which the first promoter is operably linked, and (b) a second promoter and a target gene to which the second promoter is operably linked, thereby resulting in a change to the circadian cycle of the cyanobacteria that increases expression of a target gene, wherein the second promoter is regulated by a clock signal-transmitting gene, wherein the target gene is not luciferase, and wherein the photosynthetic organism comprises a clock signal-transmitting gene under the control of an expression control sequence, wherein the clock-signal transmitting gene exhibits altered activity as compared to the natural photosynthetic organism. 
     
     
         2 . The method of  claim 1 , wherein the photosynthetic organism is a plant. 
     
     
         3 . The method of  claim 1 , wherein the photosynthetic organism is a photoautotrophic or photoheterotrophic bacteria. 
     
     
         4 . The method of  claim 1 , wherein the photosynthetic organism is a cyanobacteria. 
     
     
         5 . The method of  claim 4 , wherein the cyanobacteria is  Synechococcus elongatus.    
     
     
         6 . The method of  claim 1 , wherein the clock gene is selected from the group consisting of KaiA, KaiB, and KaiC. 
     
     
         7 . The method of  claim 1 , wherein the clock signal-transmitting gene is SasA, CikA, LabA, RpaA, or RpaB. 
     
     
         8 . The method of  claim 1 , wherein modulation of the clock signal-transmitting gene exhibits altered expression and the expression control sequence comprises a knockout mutation or a sequence mutation that alters the activity of clock signal-transmitting gene, wherein the clock gene is selected from KaiA, KaiB, and KaiC (SEQ ID NO: 3, SEQ ID NO: 4, and SEQ ID NO: 5) and the clock signal-transmitting gene is selected from SasA, CikA, LabA, RpaA and RpaB. 
     
     
         9 . The method of  claim 1 , wherein the clock signal-transmitting gene comprises a deletion mutation. 
     
     
         10 . The method of  claim 9 , wherein deletion mutation is a knock out. 
     
     
         11 . The method of  claim 1 , wherein modulating expression of a clock gene suppresses the circadian rhythm of the photosynthetic organism. 
     
     
         12 . The method of  claim 1 , wherein the target gene is a biofuel product or biofuel precursor expressing gene. 
     
     
         13 . The method of  claim 1 , wherein the photosynthetic organism is a transgenic photosynthetic organism, and the target gene is a heterologous gene. 
     
     
         14 . The method of  claim 13 , wherein the heterologous gene is a hydrogenase expressing gene. 
     
     
         15 . The method of  claim 13 , wherein the heterologous gene is a pro-insulin expressing gene. 
     
     
         16 . A photosynthetic organism having a modified circadian cycle, comprising a photosynthetic organism that has been transformed to with (a) a first promoter and a clock gene, wherein the first promoter results in overexpression of the clock gene to which the first promoter is operably linked, and (b) a second promoter and a target gene to which the second promoter is operably linked, thereby resulting in a change to the circadian cycle of the cyanobacteria that increases expression of a target gene, wherein the second promoter is regulated by a clock signal-transmitting gene, wherein the target gene is not luciferase, and wherein the photosynthetic organism underexpresses a clock signal-transmitting gene as compared to the natural photosynthetic organism. 
     
     
         17 . The photosynthetic organism of  claim 16 , wherein the photosynthetic organism is a plant. 
     
     
         18 . The photosynthetic organism of  claim 16 , wherein the photosynthetic organism is a photoautotrophic or photoheterotrophic bacteria. 
     
     
         19 . The photosynthetic organism of  claim 18 , wherein the clock gene is selected from the group consisting of KaiA, KaiB, and KaiC. 
     
     
         20 . The photosynthetic organism of  claim 16 , wherein modulating expression of a clock gene suppresses the circadian rhythm of the photosynthetic organism. 
     
     
         21 . The photosynthetic organism of  claim 16 , wherein the target gene is a gene influencing the expression of a biofuel product or biofuel precursor. 
     
     
         22 . The photosynthetic organism of  claim 16 , wherein the photosynthetic organism is a transgenic photosynthetic organism, and the target gene is a heterologous gene. 
     
     
         23 . The method of  claim 16 , wherein the clock signal-transmitting gene is SasA, CikA, LabA, RpaA, or RpaB.