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Figure 5 | BMC Microbiology

Figure 5

From: The type III secretion system is necessary for the development of a pathogenic and endophytic interaction between Herbaspirillum rubrisubalbicans and Poaceae

Figure 5

Light microscopy (LM) and transmission electron microscopy (TEM) of sugarcane leaf blades variety B-4362 inoculated with H. rubrisubalbicans M1, TSE and TSN. (a) Transversal section showing the regular tissue organization of a control plant. (ep) epidermis layer, (px) protoxylem, (ph) phloem, (mx) metaxylem, (bu) buliform cells, (arrows) bundle sheath layer with healthy chloroplasts. (b) Detailed view of the bundle sheath layer (bs) showing its chloroplasts (cl) with regular shape, distribution and appearance (arrows), and (pc) parenchyma cells. (c) Typical pattern of colonization of H. rubrisubalbicans strain M1 (wild type) showing tissue system changes associated with extensive colonization of the intercellular spaces of the mesophyll and sub-stomatal cavity (white arrows). Note the chloroplast degradation (black arrow), (vb) vascular bundles, (bs) bundle sheath, (st) stomata. (d) Detailed view of the apoplastic colonization by the wild type M1 (white arrow) and beneath the stomata cavity (black arrow). Note the bacteria surrounded by toluidine blue-stained gums. (ep) epidermis. (e) Transversal section showing TSE and TSN mutants colonizing the leaf blade. Note the plant gums which restrict the intercellular spreading of the bacterial mutants (black arrow). (f) Transversal section of localized areas densely colonized by the mutants (white arrows) showing minor anatomical changes compared with panels (a) and (c). Note the reduced numbers and size of the bundle sheath chloroplasts (black arrow). (g) Transmission electron microscopy of the mutant bacteria colonizing the intercellular spaces of mesophyll cells. See changes in the cytoplasm of the plant host cell in close contact with the bacteria. (pc) parenchyma cells. Three plants of each condition were used for microscopy and the pictures are representative of the three inoculated plants.

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