Colonization of endophyte Pantoea agglomerans YS19 on host rice, with formation of multicellular symplasmata

Pantoea agglomerans YS19 is a diazotrophic endophyte isolated from rice (Oryza sativa cv. Yuefu) grown in a temperate-climatic region in west Beijing (China). The colonization of YS19 on host rice was studied in this paper. It was revealed that YS19 colonizes in all the tissues of rice seedlings, including roots (dominantly at elongation regions, lateral root junctions, root hairs and root caps), stems and leaves. More YS19 colonizes in stem and leaves (1.40 × 10⁵ CFU mg^-1 fresh weight) than that in roots (3.60 × 10⁴ CFU mg^-1). Symplasmata, a kind of adaptive structure of the strain for its endophytic living, were repeatedly observed to form inside root or stem cortex parenchyma tissues, as well as on leaf surfaces and also rhizoplanes. A novel matrix protein (SPM43.1) with its expression paralleling to the formation of symplasmata was captured, whose meaning in structural construction of symplasmata was also discussed.