BpNAC012 Positively Regulates Abiotic Stress Responses and Secondary Wall Biosynthesis
BpNAC012 Positively Regulates Abiotic Stress Responses and Secondary Wall Biosynthesis
复制标题
DOI：
10.1104/pp.18.01167
复制
发表时间：
2019-02-01
期刊：
影响因子：
7.4
通讯作者：
Yang, Chuanping
中科院分区：
文献类型：
--
作者：
Hu, Ping;Zhang, Kaimin;Yang, Chuanping
NAC（NAM、ATAF 1/2和CUC 2）转录因子在植物的生物学过程和逆境应答中起着重要作用。在这里，我们表征了BpNAC 012在白色白桦（白桦）中的功能作用。我们发现BpNAC 012作为转录激活因子。功能获得和功能丧失分析显示，BpNAC 012的转录水平与盐和渗透胁迫耐受性呈正相关。BpNAC 012激活核心序列CGT[G/A]以诱导非生物胁迫响应下游基因的表达，包括Delta-1-吡咯啉-5-羧酸合成酶、超氧化物歧化酶和过氧化物酶，导致BpNAC 012过表达转基因桦树系的盐和渗透胁迫耐受性增强。我们还表明，BpNAC 012主要在成熟茎中表达，RNA干扰诱导的抑制BpNAC 012引起茎纤维次生壁增厚急剧减少。BpNAC 012的过表达通过直接结合次生壁NAC结合元件位点激活次生壁相关下游基因的表达，导致茎表皮中的异位次生壁沉积。此外，盐和渗透胁迫引起更高的表达水平的木质素生物合成基因和升高的木质素积累在BpNAC 012过表达株系。这些发现提供了深入了解NAC转录因子的功能。
NAC (NAM, ATAF1/2, and CUC2) transcription factors play important roles in plant biological processes and stress responses. Here, we characterized the functional roles of BpNAC012 in white birch (Betula platyphylla). We found that BpNAC012 serves as a transcriptional activator. Gain-and loss-of-function analyses revealed that the transcript level of BpNAC012 was positively associated with salt and osmotic stress tolerance. BpNAC012 activated the core sequence CGT[G/A] to induce the expression of abiotic stress-responsive downstream genes, including Delta-1-pyrroline-5-carboxylate synthetase, superoxide dismutase, and peroxidase, resulting in enhanced salt and osmotic stress tolerance in BpNAC012 overexpression transgenic birch lines. We also showed that BpNAC012 is expressed predominantly in mature stems and that RNA interference-induced suppression of BpNAC012 caused a drastic reduction in the secondary wall thickening of stem fibers. Overexpression of BpNAC012 activated the expression of secondary wall-associated downstream genes by directly binding to the secondary wall NAC-binding element sites, resulting in ectopic secondary wall deposition in the stem epidermis. Moreover, salt and osmotic stresses elicited higher expression levels of lignin biosynthetic genes and elevated lignin accumulation in BpNAC012 overexpression lines. These findings provide insight into the functions of NAC transcription factors.