Shipon Das Gupta - AG Westhoff

Characterization of leaf specific promoter and mutational analysis of leaf anatomy    

C4 photosynthesis is a high-efficiency type of photosynthesis and characterized by a division of labor between two different leaf cell types, mesophyll (M) and bundles-sheath (BS) cells. One of the key proteins in C4 photosynthesis pathway is the phosphoenol pyruvate carboxylase (PEPC) enzyme, exclusively located in the M cells and catalyzes initial fixation of CO2 into a C4 compound.  It has been found that isolated PEPC promoters from the Panicoidea C4 grass species Zea mays, Setaria viridis, Panicum miliaceum and Urochola maxima are active in C3 rice plant. Promoter-reporter analysis of these four C4 PEPC promoters in rice revealed that the promoters are specific for only M cells expression (S. Schulze, S. Karki, M. Levey, C. Blum unpublished data). However, these isolated four C4 promoters are huge in size, as they have been obtained through genome walking technique. Therefore, the cis regulatory elements responsible for the M cells specific expression of these promoters are yet to be resolved. The first object of this project is to characterize and delimit the minimal cis regulatory elements of these four C4-PEPC promoters essential for the M cell specific expression.

In C3 plants, 90% of the total chloroplast are located in the M cells within the leaf, therefore, the entire system of photosynthesis take place in the M cell, (Yoshimura et al. 2004). In contrast, C4 plants contain equal number of chloroplast in the BS and M cells. This is because; photosynthesis in C4 plants is compartmentalized into M cells and BS cells. To carry out this complex process, C4 plants adapted enlarged BS cells with more chloroplast thereby making the BS cells more pronounced and photosynthetically active. As a consequence, C4 plants possess a special kind of leaf anatomy with a wreath like structure of mesophyll and bundle sheath cells around the vascular bundles. This typical structure of C4 plants is known as Kranz anatomy characterized by the dense vein spacing with the reduced volume of M cells in relative to BS cells. Hence, the ratio between the M and BS cells reach one to one in C4 grasses. High vein densities in C4 grasses appeared due to changes in the patterning of minor not the major veins (Ueno et al., 2006). However, the genetic components regulating the alteration of leaf anatomy in the C4 plants remains poorly understood. Our second aim of this project is to change leaf anatomy of C3 plant Arabidopsis in order to identify the genes responsible for C4 Kranz anatomy evolution by taking advantage of forward genetics.

 

Starting date: 15.12.2014 / PhD student

Thesis committee members: Peter Westhoff, Rüdiger Simon

Mini Academic CV:

  •  2014
    • Master of Science (M. Sc.) at University of Bonn
      Thesis: Characterization of endoplasmic reticulum oxidoreduxtase1 (ERO1) from Arabsidopsis thaliana: Subcellular localization and functional characterization of plant specific cysteine residues   
  • 2011
    • Bachelor of Science (B. Sc.) in Genetic Engineering and Biotechnology at University of Chittagong, Bangladesh 
Photo of Shipon  Das Gupta

Shipon Das Gupta

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