Key Laboratory for Forest Genetic and Tree Improvement and Propagation in Universities of Yunnan Province, Southwest Forestry University, Kunming 650224, China; Institute of Jiangxi Oil-tea Camellia, Jiujiang University, Jiujiang 332005, China.
Key Laboratory for Forest Genetic and Tree Improvement and Propagation in Universities of Yunnan Province, Southwest Forestry University, Kunming 650224, China; Key Laboratory of Biodiversity Conservation in Southwest China, State Forestry Administration, Southwest Forestry University, Kunming 650224, China.
Gene. 2021 Mar 10;772:145349. doi: 10.1016/j.gene.2020.145349. Epub 2020 Dec 15.
Inverted cuttings of Populus yunnanensis are characterized by enlarged stems and dwarfed new shoots, and phytohormones play a crucial role in the response to inversion. The polar auxin transport (PAT) system is distinct from the transport systems of other hormones and is controlled by three major transporter gene families: pin-formed (PIN), auxin-resistant/like aux (AUX/LAX) and ATP-binding cassette transporters of the B class (ABCB). Here, we identified these three families in P. trichocarpa, P. euphratica and P. yunnanensis through a genome-wide analysis. The Populus PIN, AUX/LAX and ABCB gene families comprised 15, 8 and 31 members, respectively. Most PAT genes in Populus and Arabidopsis were identified as clear sister pairs, and some had unique motifs. Transcriptome profiling revealed that the expression of most PAT genes was unrelated to cutting inversion and that only several genes showed altered expression when cuttings were inverted. The auxin content difference at positions was opposite in upright and inverted cutting bodies during rooting, which obeyed the original plant polarity. However, during plant growth, the two direction types exhibited similar auxin movements in the cutting bodies, and the opposite auxin changes were observed in new shoots. Four PAT genes with a positive response to cutting inversion, PyuPIN10, PyuPIN11, PyuLAX6 and PyuABCB27, showed diverse expression patterns between upright and inverted cuttings during rooting and plant growth. Furthermore, PAT gene expression retained its polarity, which differs from the results found for auxin flow during plant growth. The inconformity indicated that a new downward auxin flow in addition to the old upward flow might be established during the growth of inverted cuttings. Some highly polar PAT genes were involved in the maintenance of original auxin polarity, which might cause the enlarged stems of inverted cuttings. This work lays a foundation for understanding the roles of auxin transport in plant responses to inversion.
云南杨倒插苗的特征是茎部膨大，新梢矮小，植物激素在响应倒插中起着关键作用。极性生长素运输（PAT）系统与其他激素的运输系统不同，由三个主要的转运体基因家族控制：PIN 形成蛋白（PIN）、生长素抗性/类似 aux（AUX/LAX）和 ABCB 类 ATP 结合盒转运体。在这里，我们通过全基因组分析鉴定了这三个家族在山杨、胡杨和云南杨中的存在。山杨、胡杨和云南杨的 PIN、AUX/LAX 和 ABCB 基因家族分别包含 15、8 和 31 个成员。杨树和拟南芥中的大多数 PAT 基因被鉴定为明显的姐妹对，并且有些具有独特的基序。转录组分析显示，大多数 PAT 基因的表达与切割倒插无关，只有少数基因在切割倒插时表达发生改变。在生根过程中，直立和倒插插条体中生长素含量的差异位置相反，这遵循植物原有的极性。然而，在植物生长过程中，两种方向类型的插条体中生长素的移动表现出相似的模式，新梢中观察到相反的生长素变化。对切割倒插有正向响应的四个 PAT 基因 PyuPIN10、PyuPIN11、PyuLAX6 和 PyuABCB27，在生根和植物生长过程中，直立和倒插插条之间表现出不同的表达模式。此外，PAT 基因表达保留了极性，这与植物生长过程中生长素流动的结果不同。这种不一致表明，在倒插生长过程中，除了旧的向上生长素流动外，可能会建立新的向下生长素流动。一些高度极性的 PAT 基因参与维持原始生长素极性，这可能导致倒插插条的茎部膨大。这项工作为理解生长素运输在植物响应倒插中的作用奠定了基础。
