Phylogenetic shadowing and chromatin accessibility data suggested that essential regulatory elements are absent in the 2.9 kb immediate upstream region of the published WOX4_pro::YFP cambium marker. Inclusion of an additional 6.3 kb of upstream promoter sequence and confocal imaging with different fluorophores in transgenic Arabidopsis lines revealed a much wider cell-type-specific expression pattern in parenchymous cells of the aerial plant body. The previously demonstrated activity of the WOX4_pro::YFP marker in the cambium of vascular strands in the young Arabidopsis inflorescence stem depicts only sectors of a circular subcortical layer of parenchymous AtWOX4-positive cells. Transcription starts in subepidermal cells within the inflorescence apex in a phyllotactic pattern and extends into successively branching lateral organs, which are connected via small tube-like domains of AtWOX4-expressing cells with the circular subcortical parenchymal layer that extends basipetally down the stem. AtWOX4 expression is most dynamic in leaves, where promoter activity is observed transiently at the adaxial side of the lamina and remains detectable later in the palisade parenchyma, although at a weaker level than in the vasculature. In the root the extended AtWOX4 promoter is active through the proximal root meristem, i.e. in the quiescent centre (QC) and its surrounding initials, a pattern that is broader than transcription of its stem cell promoting relative AtWOX5 in the QC. Outside the proximal meristem AtWOX4 transcription is observed in upper cell layers of the columella root cap beneath or above within the stele in proto- and metaxylem cells, in a ribbon-type pattern which divides the central cylinder in two equal halves. This xylem-specific expression it the root stele relates to established AtWOX4 activity in xylem parenchyma specificity within vascular bundles of the stem.

系统发育阴影和染色质可及性数据表明，在已发布的WOX4 _pro ::YFP形成层标记的 2.9 kb 直接上游区域中不存在必需的调节元件。在转基因拟南芥系中包含额外的 6.3 kb 上游启动子序列和不同荧光团的共聚焦成像，揭示了气生植物体薄壁细胞中更广泛的细胞类型特异性表达模式。先前证明的WOX4 _pro ::YFP标记在年轻拟南芥花序茎中维管束形成层中的活性仅描绘了实质AtWOX4的圆形皮层下层的部分-阳性细胞。转录从花序顶端内的表皮下细胞以叶序模式开始，并延伸到连续分枝的侧器官，这些侧器官通过表达AtWOX4的细胞的小管状结构域与沿茎基叶向下延伸的圆形皮层下实质层相连。AtWOX4 的表达在叶子中最为动态，在叶片的近轴侧瞬时观察到启动子活性，并且稍后在栅栏薄壁组织中仍可检测到，尽管其水平低于脉管系统。在根中扩展AtWOX4启动子通过近端根分生组织活跃，即在静止中心 (QC) 及其周围的起始处，这种模式比其在 QC 中促进相对AtWOX5 的干细胞转录更广泛。在近端分生组织外AtWOX4转录在原始和后木质部细胞中的石柱内或上方的小柱根冠的上层细胞层中观察到，呈带状模式，将中央圆柱体分成两个相等的一半。这种木质部特异性表达与根石碑相关，与茎维管束内木质部薄壁组织特异性中已建立的AtWOX4活性有关。