The role of mitogen-activated protein kinases MPK4 and MPK12 in CO2-induced stomatal movements
Date
2019-05-27
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Abstract
Taimed on elu aluseks Maal. Nad toodavad süsihappegaasist ja veest fotosünteesi käigus orgaanilisi ühendeid ning kõrvalsaadusena vabaneb ka loomseks eluks vajalik hapnik. Õhulõhed on taimelehel asuvad avad, mille kaudu toimub taime gaasivahetus ümbritseva keskkonnaga. Iga õhulõhe on ääristatud kahe sulgrakuga, mis reguleerivad õhulõhede avanemist ja sulgumist. Õhulõhede avanemise põhjustab valgus, madal CO2 kontsentratsioon ja kõrge õhuniiskus, sulgumise aga pimedus, kõrge CO2 kontsentratsioon, madal õhuniiskus, taimehormoonid, patogeenid ja õhu saasteained. Õhulõhede avanemine soodustab taime kasvu, kuna avatud õhulõhede kaudu jõuab taime fotosünteesiks vajalik CO2, samas aga suureneb ka vee aurustumine taimest, mis põuatingimustes võib viia taime närbumiseni. Seetõttu on õhulõhede avatuse täpne regulatsioon ülioluline, optimeerimaks taime kasvu erinevates stressitingimustes. Suurenev CO2 kontsentratsioon atmosfääris vähendab õhulõhede avatust ja vee aurustumist taimest. Kuidas aga toimub sulgrakkudes CO2 mõjul signaaliülekanne, mis viib õhulõhede sulgumiseni, pole praegusel ajal veel täpselt teada. Antud töö tulemused aitavad mõista, kuidas taimed reguleerivad õhulõhede avatust CO2 kontsentratsiooni muutuse toimel. Töö käigus tehti kindlaks, et mitogeen-aktiveeritud proteiinkinaasid, MPK4 ja MPK12, on ühtedeks varaseimateks komponentideks signaaliülekanderajas, mis viib kõrge [CO2] mõjul õhulõhede sulgumiseni. Töö käigus saadud teadmiste põhjal pakuti välja ka mudel MPK4 ja MPK12 rolli kohta õhulõhede vastuses CO2 kontsentratsiooni muutustele. Antud töö tulemused aitavad kaasa selliste toidutaimede aretamisele, mis oleksid piisavalt saagikad ka tulevikukliimas, kõrgema atmosfääri CO2 kontsentratsiooni ja piiratud veevarude tingimustes.
Plants are essential to life on Earth – in the process of photosynthesis, they convert carbon dioxide (CO2) and water into organic compounds, and oxygen is released as a by-product. Stomatal pores, that are on the surfaces of the majority of the aerial parts of plants, facilitate gas exchange between plants and the external atmosphere. Each stomatal pore is surrounded by two highly specialized guard cells which sense various endogenous and environmental stimuli, such as CO2, light, temperature, hormones and pathogens and adjust the stomatal pore size to balance CO2 uptake for photosynthesis and loss of water vapour through transpiration. Since water availability is a major constraint of crop yield and is the single most important factor limiting food production, appropriate control of stomatal pore size is essential for the optimization of plant growth. Continuing rise in atmospheric [CO2] increases [CO2] inside the leaves and causes a reduction in stomatal apertures. This, in turn, reduces water loss from plants. Thus, CO2-induced stomatal closure may improve plant water use efficiency and optimization of CO2-controlled stomatal movements may enable breeding of crops that conserve water while maximizing photosynthesis. Presently, the molecular mechanisms by which plants sense CO2 concentration and transduce the CO2 signal to regulate water loss, are not fully understood. This thesis contributes to the understanding of the mechanism how the CO2 signal is transduced in the guard cells and proposes a new model for stomatal CO2-signalling. This study revealed that mitogen-activated protein kinases (MPKs) MPK4 and MPK12 are among the earliest CO2 signalling components presently known in guard cells and that CO2-signal is transmitted through MPK4 and MPK12 leading to activation of guard cell anion channels and closing of stomata. With the continuous increase in atmospheric CO2 levels and the need for breeding crops that would display optimal water use efficiencies, these findings are important for developing strategies for breeding crops suitable for future climates by specific modulation of CO2-dependent stomatal movements.
Plants are essential to life on Earth – in the process of photosynthesis, they convert carbon dioxide (CO2) and water into organic compounds, and oxygen is released as a by-product. Stomatal pores, that are on the surfaces of the majority of the aerial parts of plants, facilitate gas exchange between plants and the external atmosphere. Each stomatal pore is surrounded by two highly specialized guard cells which sense various endogenous and environmental stimuli, such as CO2, light, temperature, hormones and pathogens and adjust the stomatal pore size to balance CO2 uptake for photosynthesis and loss of water vapour through transpiration. Since water availability is a major constraint of crop yield and is the single most important factor limiting food production, appropriate control of stomatal pore size is essential for the optimization of plant growth. Continuing rise in atmospheric [CO2] increases [CO2] inside the leaves and causes a reduction in stomatal apertures. This, in turn, reduces water loss from plants. Thus, CO2-induced stomatal closure may improve plant water use efficiency and optimization of CO2-controlled stomatal movements may enable breeding of crops that conserve water while maximizing photosynthesis. Presently, the molecular mechanisms by which plants sense CO2 concentration and transduce the CO2 signal to regulate water loss, are not fully understood. This thesis contributes to the understanding of the mechanism how the CO2 signal is transduced in the guard cells and proposes a new model for stomatal CO2-signalling. This study revealed that mitogen-activated protein kinases (MPKs) MPK4 and MPK12 are among the earliest CO2 signalling components presently known in guard cells and that CO2-signal is transmitted through MPK4 and MPK12 leading to activation of guard cell anion channels and closing of stomata. With the continuous increase in atmospheric CO2 levels and the need for breeding crops that would display optimal water use efficiencies, these findings are important for developing strategies for breeding crops suitable for future climates by specific modulation of CO2-dependent stomatal movements.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
taimefüsioloogia, süsinikdioksiid, toime, õhulõhed, regulatsioon (biol.), signaali transduktsioon, proteiinkinaasid