Ko Jae-Heung, Prassinos Constantinos, Han Kyung-Hwan
Department of Forestry, Michigan State University, 126 Natural Resources, East Lansing, MI 48824-1222, USA.
New Phytol. 2006;169(3):469-78. doi: 10.1111/j.1469-8137.2005.01623.x.
In contrast to our knowledge of the shoot apical meristem, our understanding of cambium meristem differentiation and maintenance is limited. Class III homeodomain leucine-zipper (HD-Zip) proteins have been shown to play a regulatory role in vascular differentiation. The hybrid aspen (Populus tremulaxPopulus alba) class III HD-Zip transcription factor (PtaHB1) and microRNA 166 (Pta-miR166) family were cloned from hybrid aspen using a combination of in silico and polymerase chain reaction methods. Expression analyses of PtaHB1 and Pta-miR166 were performed by Northern blot analysis. The expression of PtaHB1 was closely associated with wood formation and regulated both developmentally and seasonally, with the highest expression during the active growing season. Also, its expression was inversely correlated with the level of Pta-miR166. Pta-miR166-directed cleavage of PtaHB1 in vivo was confirmed using modified 5'-rapid amplification of cDNA ends (RACE). The expression of Pta-miR166 was much higher in the winter than in the growing seasons, suggesting seasonal and developmental regulation of microRNA in this perennial plant species.
与我们对茎尖分生组织的了解相比，我们对形成层分生组织分化和维持的认识有限。III类同源异型域亮氨酸拉链（HD-Zip）蛋白已被证明在维管分化中起调节作用。利用电子克隆和聚合酶链反应相结合的方法，从杂种山杨中克隆了III类HD-Zip转录因子（PtaHB1）和微小RNA 166（Pta-miR166）家族。通过Northern杂交分析对PtaHB1和Pta-miR166进行表达分析。PtaHB1的表达与木材形成密切相关，在发育和季节上都受到调控，在活跃生长季节表达量最高。此外，其表达与Pta-miR166的水平呈负相关。使用改良的5'-cDNA末端快速扩增（RACE）技术在体内证实了Pta-miR166对PtaHB1的切割作用。Pta-miR166在冬季的表达远高于生长季节，这表明在这种多年生植物物种中微小RNA受到季节和发育的调控。
