《植物细胞解剖学》课程教学资源（PPT）13

Heat stress nGaannTTCnnGAAn⊥DNA Heat shock element HSP70 Heat shock protein mRNA ∩QQ Heat factor (HSF) Heat shock F oteins Igure (HSP) FIGURE 25. 11 The heat shock factor(HSF)cycle activates leading to the translation of HSPs among which are HSP70 the synthesis of heat shock protein mRNAs In nonstressed (4). The HSF trimers associated with the HSE are phospho- cells, HSF normally exists in a monomeric state()associ- rylated (5) facilitating the binding of HSP70 to the phos- ated with HSP70 proteins. Upon the onset of an episode of phorylated trimers(6). The HSP70 trimer complex(7)disso- heat stress, HSP70 dissociates from HSF which subse- ciates from the HSE and disassembles and dephosphory quently trimerizes(2). Active trimers bind to heat shock lates into HSF monomers(8), which subsequently bind HSP elements(HSE)in the promoter of heat shock protein(HSP) reforming the resting HSP70/HSF complex (After Bray et genes(3), and activate the transcription of HSP mRNAs al.2000.)

Figure 13-6

X MEnie FIGURE 25.18 Scanning electron micrographs of transverse nent gas-filled spaces (gs) in the cortex(ex), formed by sections through roots of maize, showing changes in struc. degeneration of cells, The stele (all cells interior to the ture with oxygen supply. ( 150x)(A)Control root, supplied endodermis, En)and the epidermis(Ep)remain intact. X, with air, with intact cortical cells. (B)Oxygen-deficient root xylem. Courtesy of ). L. Basq and M C Drew. growing in a nonaerated nutrient solution. Note the promi- Figure 13-7

Figure 13-7

OUTSIDE OF CELL Pathogen Elicitor(product of an avr gene) Cell wall 0,-, Reactive oxyge Cell wall species cross-linking NADPH oxidase Plasma membrane Receptor Ion fluxes (R gene Activation of genes for change in roduct Hypersensitive response membrane otential-> Phytoalexin biosynthesis Lignin biosynthesis Systemic Salicylic acid biosynthesis-+acquired Biosynthesis of hydrolytic resistance CYTOPLASM enzymes Figure 13-9 FIGURE 13.25 Many modes of antipathogen defense are induced by infection Fragments of pathogen molecules called elicitors initiate a complex signaling path way leading to the activation of defensive responses. Some bacterial protein elici tors are injected directly into the cell, where they interact with R gene products

Figure 13-9

ure Oxides of sulfur emitted from fossil fuel power plants and other industries, and oxides of nitrogen from automobile exhaust, are converted in the moist atmosphere into acids that become dispersed over wide areas. Unlike unpolluted rain (average pH 5.6), the ph of acid rain has been measured at 4.2 and even lower. Plants, such as these trees photographed in the Black Forest of germany, may be damaged when the resulting increase in soil acidity causes certain minerals, particularly calcium ions, to leach out of the soil. (Hans Reinhard/Bruce Coleman)

Figure 13-10