Funkcje fizjologiczne chloroplastowej proteazy AtDeg5
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2015-06-19
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Physiological functions of chloroplast protease AtDeg5
Abstract
Chloroplastowe białko AtDeg5 jest proteazą typu serynowego peryferycznie zasocjowaną z błoną od strony światła tylakoidu. Ze względu na słabo poznaną rolę, jaką odgrywa AtDeg5 w kontroli przebiegu procesów ontogenezy przebadano dwie niezależne linie mutantów insercyjnych o różnym stopniu wyciszenia AtDEG5 i w oparciu o stadia ontogenezy przeanalizowano szereg cech. Obie linie mutantów wykazywały kompensacyjną hiperakumulację AtDeg8. Represja proteazy AtDeg5 spowodowała zmianę wielu cech fenotypowych przynajmniej u jednego z mutantów, przy czym najbardziej znaczące zmiany dotyczyły chronologicznej progresji wzrostu i rozwoju indywidualnych liści rozetkowych, produkcji kwiatów, dojrzewania łuszczynek oraz morfologii w pełni rozwiniętych liści, ultrastruktury chloroplastów, akumulacji apobiałka Lhcb6 w chloroplastach, organizacji strukturalnej cząsteczek PSII, tworzenia rozgałęzień pędów kwiatostanowych oraz długości i szerokości nasion. W odniesieniu do cech fenotypowych regulowanych przez AtDeg5 można wnioskować, że nadmiar AtDeg8 może efektywnie kompensować deficyt 23% puli AtDeg5 lub chloroplast dysponuje nadmiarem centrów katalitycznych AtDeg5 w stosunku do potrzeb, a efekt dawki AtDeg5 odgrywa bądź nie odgrywa istotnej roli. Alternatywnie nadmiar AtDeg8 nie kompensuje deficytu 23%puli AtDeg5, a chloroplast nie dysponuje nadmiarem centrów katalitycznych AtDeg5 w stosunku do potrzeb.
The chloroplast protein AtDeg5 is a serine-type protease peripherally attached to thylakoid membrane at its lumenal side. Since reliable data regarding the role of AtDeg5 in controlling the course of growth and developmental processes are extremely limited, two independent T-DNA insertional lines with different extent of AtDeg5 reduction were prepared and ontogenesis stage-based analysis performed. Both mutant lines displayed a compensatory overaccumulation of AtDeg8. The repression of AtDeg5 protease altered a range of phenotypic features in at least one of the mutants, with the most prominent being changes in chronological progression of development and growth of individual rosette leaves, flower production, silique ripening and in the morphology of fully expanded leaves, chloroplast ultrastructure, starch metabolism in chloroplasts, accumulation of Lhcb6 apoprotein in chloroplasts and structural organization of PSII molecules as well as in formation of inflorescence debranching and in length and width of seeds. By analyzing the results of parallel-mutant screening we conclude that AtDeg8 overdose may rescue 23% of AtDeg5 deficiency with regard to some AtDeg5-controlled traits; alternatively AtDeg5 may have catalytic sites in excess so that these traits might remain unaltered when AtDeg5 pool is reduced by 23%. For some other AtDeg5-dependent traits the absence of excessive amount of AtDeg5 catalytic sites, lack of AtDeg5 dosage effect and inability of AtDeg8 to compensate deficiency or absence of AtDeg5 occurred.
The chloroplast protein AtDeg5 is a serine-type protease peripherally attached to thylakoid membrane at its lumenal side. Since reliable data regarding the role of AtDeg5 in controlling the course of growth and developmental processes are extremely limited, two independent T-DNA insertional lines with different extent of AtDeg5 reduction were prepared and ontogenesis stage-based analysis performed. Both mutant lines displayed a compensatory overaccumulation of AtDeg8. The repression of AtDeg5 protease altered a range of phenotypic features in at least one of the mutants, with the most prominent being changes in chronological progression of development and growth of individual rosette leaves, flower production, silique ripening and in the morphology of fully expanded leaves, chloroplast ultrastructure, starch metabolism in chloroplasts, accumulation of Lhcb6 apoprotein in chloroplasts and structural organization of PSII molecules as well as in formation of inflorescence debranching and in length and width of seeds. By analyzing the results of parallel-mutant screening we conclude that AtDeg8 overdose may rescue 23% of AtDeg5 deficiency with regard to some AtDeg5-controlled traits; alternatively AtDeg5 may have catalytic sites in excess so that these traits might remain unaltered when AtDeg5 pool is reduced by 23%. For some other AtDeg5-dependent traits the absence of excessive amount of AtDeg5 catalytic sites, lack of AtDeg5 dosage effect and inability of AtDeg8 to compensate deficiency or absence of AtDeg5 occurred.
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Wydział Biologii: Instytut Biologii Eksperymentalnej
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Proteaza AtDeg5, Protease AtDeg5, chronologiczna progresja, chronological progression, morfologia liści, leaf morphology, ultrastruktura chloroplastów, chloroplast ultrastructure, ziarna skrobi, starch grains