Infection of maize leaves with Ustilago maydis prevents establishment of C4 photosynthesis

A model ofUstilago maydisleaf tumor metabolism

“…However, at 8 dpi, maize plastidic protein biosynthesis is transcriptionally repressed, but cytosolic protein biosynthesis is induced on the transcript level ( Table 1). Despite the fact that plastids of tumor cells carry a reduced photosynthetic apparatus compared to control leaves that requires less protein maintenance, 2,3 this suggests that the increased availability of providing carbon backbones for many AA. 9 The nitrogen-rich AA asparagine accumulates and is specifically synthesized by asparagine synthetase in tumors, 5 which indicates high nitrogen availability for tumor cells.…”

“…While reduced plastidic protein biosynthesis reflects the reduction of photosynthetic rates in tumors and galls 2,11 increased cytosolic protein biosynthesis could reflect the induction of host PR protein biosynthesis. Even in the compatible interaction between U. maydis and maize, the pathogen induces a defense reaction, including the strong transcriptional induction of pathogenesis related (PR) genes 3 and it has been shown that ribosomes produce large amounts of PR proteins during pathogen attack.…”

“…1 It was shown that by inducing tumors on maize (Zea mays) leaves, the biotrophic basidiomycete fungus Ustilago maydis establishes a strong sink organ for carbohydrates [2][3][4] and amino acids. 5 These assimilates are provided by systemic source leaves, which exhibit increased productivity and increased export rates compared to comparable leaves of non-infected maize plants.…”

“…3 At the same time, tumor metabolism is characterized by reduced photosynthesis and an accumulation of soluble sugars, i.e., hexoses which are generated via cleavage of sucrose by cell wall and vacuolar invertases. 2 In addition, a plasmamembrane-associated sucrose synthase (Sus1) 6 is six-fold induced in tumors. Thus, we propose that sucrose imported from systemic leaves into tumor tissue serves the following main functions in host and pathogen metabolism: (1) provision of building blocks for cell wall biosynthesis of the tumor cell, which is channeled by SUS1, (2) generation of hexoses in the tumor-cell vacuole to build up osmotic pressure for tumor cell-expansion (see Fig.…”

An Overview of Plant Photosynthesis Modulation by Pathogen Attacks

“…Nontheless, many temperate plant species may not adapt as rate of photosynthesis was found to decline at moderately high temperature in a temperate species such as Arabidopsis thaliana (Kumar et al, 2009, Kurek et al, 2007. If CO 2 generally favours photosynthesis, other environmental clues such as UV-B (Albert et al, 2008), heat shock and water deficit (Abrams et al, 1990, Ackerson and Hebert, 1981, Allakhverdiev et al, 2008, ZhangWollenweber et al, 2008), Cold (Batista-Santos et al, 2011, Bilska and Sowinski, 2010, herbivore and pathogen attacks have detrimental effects on photosynthesis (Halitschke et al, 2011, Horst et al, 2008, King and Caylor, 2010, Nabity et al, 2009). The primary targets of thermal damage in plants are the oxygen evolving complex along with the associated cofactors in photosystem II (PSII), carbon fixation by Rubisco and the ATP generating system (Allakhverdiev et al, 2008).…”