Differential Distribution of Callose and a (1→4)β‐D‐galactan Epitope in the Laticiferous Plant Euphorbia Heterophylla L.

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Euphorbia heterophylla L. produces latex in nonarticulated laticifers, which are giant, coenocytic cells that elongate indefinitely and grow intrusively between other cells. To identify characteristics that may determine the unusual growth patterns of nonarticulated laticifers, we have analyzed the composition of their cell walls using various antibodies against carbohydrate epitopes. These analyses revealed that the laticifer walls differ from those of their surrounding cells. The level of a (1→4)β‐D‐galactan epitope was much lower in laticifers than in other cells. Similarly, an anti‐(1→3)β‐D‐glucan antibody that recognizes callose did not label laticifer walls and walls immediately adjacent to laticifers, but it produced a punctuated labeling pattern in most other cells. In contrast to (1→4)β‐D‐galactan and callose, the (1→5)α‐arabinan epitope, the homogalacturonan epitopes recognized by the JIM5 and JIM7 antibodies, and xyloglucan were present at similar levels in laticifers and their surrounding cells. Furthermore, a broad homogalacturonan‐rich middle lamella was present between laticifers and adjacent cells. Comparison of the results in E. heterophylla with those previously reported for Asclepias speciosa indicate that the development of nonarticulated laticifers is associated with similar modifications in wall characteristics, even though laticifers in these species have presumably different evolutionary origins.