ZmbZIP27 regulates nitrogen-mediated leaf angle by modulating lignin deposition in maize

In grain crops such as maize(Zea mays),leaf angle(LA)is a key agronomic trait affecting light interception and thus planting density and yield.Nitrogen(N)affects LA in plants,but we lack a good understanding of how N regulates LA.Here,we report that N deficiency enhanced lignin deposition in the ligular region of maize seedlings.In situ hybridization showed that the bZIP transcription factor gene ZmbZIP27 is mainly expressed in the phloem of maize vascular bundles.Under N-sufficient conditions,transgenic maize overexpressing ZmbZIP27 showed significantly smaller LA compared with wild type(WT).By contrast,zmbzip27_(ems)mutant showed larger LA under both N-deficient and N-sufficient conditions compared with WT.Overexpression of ZmbZIP27 enhanced lignin deposition in the ligular region of maize in the field.We further demonstrated that ZmbZIP27 could directly bind the promoters of the microRNA genes ZmMIR528a and ZmMIR528b and negatively regulate the expression levels of ZmmiR528.ZmmiR528 knockdown transgenic maize displayed erect architecture in the field by increasing lignin content in the ligular region of maize.Taken together,these results indicate that ZmbZIP27 regulates N-mediated LA size by regulating the expression of ZmmiR528 and modulating lignin deposition in maize.

具叶舌痕的圆印木状茎干在安徽巢湖上泥盆统的首次发现

在描述的几块产自安徽巢湖五通组中上部（法门期）的圆印木状茎干中，首次发现其中一块标本具有明显的叶舌痕，它与另一块叶痕特征相同但不具叶舌痕的标本共生．说明它们很可能应归为同一种植物。因此叶舌痕的有无很可能与化石的保存状态有关。圆印木属与窝木属仅根据茎干叶痕特征是难于区分的。但由于这两个属的生殖部分（球果）存在差别，目前仍被视为不同的属。当前的标本未发现生殖部分，难于确定其归属。笔者建议，为了实用方便将这类发现于上泥盆统的标本，暂归为Ｂｏｔｈｒｏｄｅｎｄｒｏｎ（Ｃｙｃｌｏｓｔｉｇｍａ）属名之下，作为形态属或卫星属来处理。