在拟南芥中,韧皮部薄壁组织(PP)转移细胞(TC)中壁向内生长的极化沉积发生在筛子元素/伴随细胞(SE/CC)复合物的细胞附近。然而,小静脉中这些不同细胞类型之间的空间关系,发生韧皮部加载的地方,知之甚少。将PPTC发育和壁向内生长定位与Col-0和转基因品系AtSUC2::AtSTP9-GFP(绿色荧光蛋白)和AtSWEET11::AtSWEET11-GFP中的其他韧皮部细胞进行了比较,鉴定了CC和PP细胞,分别。小静脉中PPTC的发育,由壁向内生长的沉积表明,在叶子上进行基底化。然而,并非所有的PP细胞都会向内生长,与近端PPTC相比,abaxal中的沉积水平更高。此外,壁向内生长的沉积仅在PPTC/SE界面上开始并优先覆盖,而不是PPTC/CC接口,并且仅发生在与SE相邻的PP细胞中。总的来说,这些结果表明,在PPTC中,SE与壁向内生长沉积之间存在紧密联系,并表明在叶片小脉中存在两种PP细胞亚型。与PP细胞相比,PPTC显示出更丰富的AtSWEET11-GFP积累,表明PP和PPTC之间韧皮部负载的功能差异。
In Arabidopsis, polarized deposition of wall ingrowths in phloem parenchyma (PP) transfer cells (TCs) occurs adjacent to cells of the sieve element/companion cell (SE/CC) complex. However, the spatial relationships between these different cell types in minor veins, where phloem loading occurs, are poorly understood. PP TC development and wall ingrowth localization were compared with those of other phloem cells in leaves of Col-0 and the transgenic lines AtSUC2::AtSTP9-GFP (green fluorescent protein) and AtSWEET11::AtSWEET11-GFP that identify CCs and PP cells, respectively. The development of PP TCs in minor veins, indicated by deposition of wall ingrowths, proceeded basipetally in leaves. However, not all PP cells develop wall ingrowths, and higher levels of deposition occur in abaxial- compared with adaxial-positioned PP TCs. Furthermore, the deposition of wall ingrowths was exclusively initiated on and preferentially covered the PP TC/SE interface, rather than the PP TC/CC interface, and only occurred in PP cells that were adjacent to SEs. Collectively, these results demonstrate a tight association between SEs and wall ingrowth deposition in PP TCs and suggest the existence of two subtypes of PP cells in leaf minor veins. Compared with PP cells, PP TCs showed more abundant accumulation of AtSWEET11-GFP, indicating functional differences in phloem loading between PP and PP TCs.