Author/Editor     Brzin, Jernej
Title     Določanje fitoplazem in njihov vpliv na nekatere fiziološke procese v koruzi (Zea mays L.)
Translated title     Detection of phytoplasmas and their influence on physiological processes in maize (Zea mays L.)
Type     monografija
Place     Ljubljana
Publisher     Univerza v Ljubljani, Medicinska fakulteta
Publication year     2004
Volume     str. 129
Language     slo
Abstract     Phytoplasmas are uncultivable, wall-less and the smallest known cellular organisms related to Gram positive bacteria. They live exclusively in the sieve tubes of their plant hosts and cause several hundred important vector-borne and graft-transmissible plant diseases. Reduced translocation of photoassimilates and the accompanying plethora of the information molecules in the phloem is probably the main cause for the symptom expression. However, the cause for the reduced phloem transport remains a black box. Here we followed the colonization of maize (Zea mays L.) with maize bushy stunt phytoplasma, the pathohistological changes of the phloem and investigated the influence of phytoplasmas on the host cell energy metabolism. Phytoplasmas were present in the sieve tubes throughout the plant as confirmed by polymerase chain reaction and immunofluorescence (IF) analyses. Infected plants were stunted and leaves showed characteristic signs of sugar accumulation. Deposits of callose and accumulation of autofluorescent compounds characteristic of phenylpropanoids were observed in the sieve tubes of symptomatic leaves by fluorescence microscopy. The high energy demands for the transport process in the phloem are met by metabolism of hexoses in glycolysis and respiration, for which the prerequisite is thought to be the cleavage of sucrose to UDP-glucose and fructose by the sucrose synthase. Sucrose synthase isozyme SS1 was localized by IF exclusively in the companion cells of most plant organs, which supports the crucial role of sucrose synthase in sucrose metabolism in the phloem. Additional quantitative western blot analysis revealed several fold induction of SS1 in the midribs, leaf sheath and stem of the infected plants. This indicates higher rate of sucrose metabolism in the phloem of infected plants, which might be important for providing sufficient hexoses for the growth of phytoplasmas. (Abstract truncated at 2000 characters).
Descriptors     CORN
PLANT DISEASES
MYCOPLASMATALES
PLANT PROTEINS
ALKALINE PHOSPHATASE
POLYMERASE CHAIN REACTION
MICROSCOPY, FLUORESCENCE
BLOTTING, WESTERN
ELECTROPHORESIS, POLYACRYLAMIDE GEL
ISOENZYMES
SUCROSE