2024-03-29T12:14:32Zhttps://www.tdx.cat/oai/requestoai:www.tdx.cat:10803/4039532017-08-29T20:43:30Zcom_10803_1col_10803_12
nam a 5i 4500
Fotosíntesi
Fotosíntesis
Photosynthesis
Aigua
Agua
Water
Transport biològic
Transporte biológico
Biological transport
Synthetic engineering of membrane transport to increase photosynthesis and water use efficiency = Enginyeria sintètica del transport de membrana per tal d’augmentar la fotosíntesi i l’eficiència en l’ús de l’aigua
[Barcelona] :
Universitat de Barcelona,
2017
Accés lliure
http://hdl.handle.net/10803/403953
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Minguet Parramona, Carla,
autor
1 recurs en línia (344 pàgines)
Tesi
Doctorat
Universitat de Barcelona. Departament de Biologia Vegetal
2015
Universitat de Barcelona. Departament de Biologia Vegetal
Tesis i dissertacions electròniques
Nogués Mestres, Salvador,
supervisor acadèmic
Blatt, Michael R
(Michael Robert)
supervisor acadèmic
TDX
The rapid increase on world’s population is threatening food security, mainly in developing countries, where poverty and hunger are already a big concern. However, a growth in agriculture generates an overall economic growth and leads to a poverty reduction. The aim of this thesis was to develop synthetic biological solutions that might aid in increasing photosynthetic yields and water use efficiency of plants, thereby improving crop yields.
Two strategies were developed as a possible ways to manipulate the plant in order to get an increase on photosynthesis and water use efficiency (WUE). The first was through the engineering of a carbon concentrating mechanism (CCM) in a C3 plant, in order to reduce the oxygenase activity of Rubisco and thus increasing photosynthesis. The second was through exploring the possibilities of changing stomatal kinetics in order to put in concordance the stomatal conductance with the mesophyll demand for CO2; thus not only the possibility of increasing photosynthesis but WUE.
In order to engineer a CCM into a C3 plant it was elaborated an artificial transport system in the inner envelope of the chloroplasts that could be used to increase the levels of HCO3-‐ in the chloroplasts stroma. To this end, the light driven pump halorhodopsin from Natronomonas pharaonis (NpHR) was chosen and targeted to the inner envelope of the chloroplast with the aim to establish a Cl-‐ gradient across the chloroplasts inner envelope. The human anion exchanger, AE1, was also targeted and introduced into the inner envelope of the chloroplasts, to allow an exchange of Cl-‐ per HCO3-‐, thus powering an increase in HCO3-‐ in the chloroplast stroma. A third protein, bCMO1 was also incorporated to the system in order to provide necessary retinal for the proper activity of NpHR. Transgenic plants expressing the artificial membrane transport system were generated, however no increase on photosynthesis could be observed on the transformed plants. It might be necessary to create another synthetic system designed to retain the CO2 where the Rubisco is localised, in order for Rubisco to be able to fix it.
As possibilities to change stomatal kinetics two different approaches were studied. The first one was to manipulate the stomatal kinetics through the manipulation of the Kin channels V1/2. The second one was to manipulate the stomatal kinetics through the addition of the external pump NpHR. Both approaches were simulated on the guard cell model OnGuard. Out from the model predictions it was observed
that both approaches were able to manipulate the stomatal kinetics. By manipulating Kin channels V1/2 to more positive values related to the control, the stomata opened faster, however it remained opened during the night. In contrast, when manipulating Kin channels V1/2 to more negative values, the stomata didn’t show much variation between the day and night, thus remaining almost closed during the whole day cycle. Surprisingly, the model predicted that by adding the NpHR in the plasma membrane of the guard cell, the stomata opened faster under a light stimuli and it also closed faster under a dark stimuli. Thus, presenting behaviour that could become to an increase on plant photosynthesis and WUE if reproducible in vivo. After a complex cloning work it was possible to create transgenic plants comprising all the characteristics previously reproduced into the model. These characteristics were from both, the Kin approach, on which the KAT1 channel was the selected one in order to be modified, and the NpHR approach. Experiments on gas exchange measurements should be done in order to prove if the generated plants have an increase on photosynthesis and WUE, which hasn’t been demonstrated yet.
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