State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, Shandong, P. R. China.
State Key Laboratory of Crop Biology, College of Agronomy, Shandong Agricultural University, Tai'an, Shandong, P. R. China.
Sci Rep. 2018 Jun 11;8(1):8873. doi: 10.1038/s41598-018-27274-8.
Lipid transfer proteins (LTPs), a class of small, ubiquitous proteins, play critical roles in various environmental stresses. However, their precise biological functions remain unknown. Here we isolated an extracellular matrix-localised LTP, NtLTP4, from Nicotiana tabacum. The overexpression of NtLTP4 in N. tabacum enhanced resistance to salt and drought stresses. Upon exposure to high salinity, NtLTP4-overexpressing lines (OE lines) accumulated low Na levels. Salt-responsive genes, including Na/H exchangers (NHX1) and high-affinity K transporter1 (HKT1), were dramatically higher in OE lines than in wild-type lines. NtLTP4 might regulate transcription levels of NHX1 and HKT1 to alleviate the toxicity of Na. Interestingly, OE lines enhanced the tolerance of N. tabacum to drought stress by reducing the transpiration rate. Moreover, NtLTP4 could increase reactive oxygen species (ROS)-scavenging enzyme activity and expression levels to scavenge excess ROS under drought and high salinity conditions. We used a two-hybrid yeast system and screened seven putative proteins that interact with NtLTP4 in tobacco. An MAPK member, wound-induced protein kinase, was confirmed to interact with NtLTP4 via co-immunoprecipitation and a firefly luciferase complementation imaging assay. Taken together, this is the first functional analysis of NtLTP4, and proves that NtLTP4 positively regulates salt and drought stresses in N. tabacum.
脂质转移蛋白（LTPs）是一类小型、普遍存在的蛋白质，在各种环境胁迫中发挥着关键作用。然而，其确切的生物学功能尚不清楚。本研究从烟草中分离到一个细胞外基质定位的 LTP，命名为 NtLTP4。在烟草中过表达 NtLTP4 可增强其对盐和干旱胁迫的抗性。在高盐胁迫下，NtLTP4 过表达系（OE 系）积累的 Na 水平较低。盐响应基因，包括 Na+/H+ 交换体（NHX1）和高亲和性 K+转运体 1（HKT1），在 OE 系中表达量显著高于野生型系。NtLTP4 可能通过调节 NHX1 和 HKT1 的转录水平来减轻 Na 的毒性。有趣的是，OE 系通过降低蒸腾速率来增强烟草对干旱胁迫的耐受性。此外，NtLTP4 可以在干旱和高盐条件下通过增加活性氧（ROS）清除酶的活性和表达水平来清除过量的 ROS。我们利用双杂交酵母系统筛选了与烟草中 NtLTP4 相互作用的七个假定蛋白。一个 MAPK 成员，即创伤诱导蛋白激酶，通过共免疫沉淀和萤火虫荧光素酶互补成像实验被证实与 NtLTP4 相互作用。综上所述，这是对 NtLTP4 的首次功能分析，证明了 NtLTP4 可正向调控烟草的盐和干旱胁迫。
