IMMUNOFLUORESCENT LOCALIZATION OF RUBPCASE IN DEGRADED C-4 GRASS TISSUE

Digestion-resistant tissues found in C-4 grasses may allow soluble pro tein to escape rumen degradation. The objective of this study was to u se immunofluorescent localization to follow loss of ribulose 1,5-bisph osphate carboxylase/oxygenase (RuBPCase) from switchgrass (Panicum vir gatum L.) and big bluestem (Andropogon gerardii Vitman) parenchyma bun dle sheath cells (BSC) during rumen degradation. Fluorescent signal wa s observed from switchgrass and big bluestem BSC through 24 and 16 h i n situ digestion, respectively, and from BSC associated with both inta ct tissue fragments, and isolated vascular bundles in omasal digesta a nd fecal material from steers (Bos tarus L.) grazing switchgrass. Immu nofluorescent localization demonstrated that in certain C-4 grasses (i ) parenchyma BSC can protect RuBPCase from degradation through 24-h in situ incubation, (ii) BSC containing RuBPCase can exit the rumen prio r to degradation, and (iii) protein protected by BSC can escape degrad ation in the whole gastrointestinal tract and be excreted.