结论:与NaCl相比,NaHCO3通过下调相关基因的表达,引起红花的氧化损伤和光合作用抑制。盐碱胁迫是限制植物生长的重要因素之一。NaCl和碳酸氢钠(NaHCO3)是中性和碱性盐,分别。这项研究研究了用200mmolL-1的NaCl或NaHCO3处理的红花(CarthamustinctoriusL.)叶片的生理特性和分子响应。用NaCl处理的植物在抑制红花的生长方面效果较差,但增加了叶片中丙二醛(MDA)的含量。同时,红花通过增加脯氨酸(Pro)减轻应力损伤,可溶性蛋白(SP),和可溶性糖(SS)。当红花受到NaHCO3胁迫时,其鲜重和干重均严重下降,细胞膜通透性和渗透调节物质含量显著增加。使用基因本体论和京都基因和基因组百科全书对差异表达基因(DEGs)的富集分析确定了与氧化应激相关的光合作用和途径的显着富集。此外,加权基因共表达网络分析(WGCNA)表明,深绿模块与光合作用和氧化应激性状的相关性最高。大量的转录因子,主要来自MYB,GRAS,WRKY,和C2H2家族,是从暗绿模块内的基因预测的。对生理指标和DEG的分析,发现在盐碱胁迫下,与叶绿素合成酶相关的基因下调,虽然与降解有关的那些被上调,导致叶绿素生物合成受到抑制,叶绿素含量下降。此外,NaCl和NaHCO3胁迫下调Calvin循环相关基因的表达,光合天线蛋白,和不同程度的光合反应中心的活性,阻碍光合电子转移过程,抑制光合作用,与NaHCO3的压力造成更明显的不利影响。在氧化应激方面,NaCl处理下活性氧(ROS)水平无明显变化,但是在NaHCO3胁迫下,过氧化氢的含量和超氧阴离子的产生速率显着增加。此外,NaCl处理上调了超氧化物歧化酶(SOD)关键基因的表达水平,过氧化氢酶(CAT),过氧化物酶(POD),抗坏血酸-谷胱甘肽循环,硫氧还蛋白-过氧化物氧还蛋白途径,并增加了这些酶的活性,因此,减少氧化损伤。同样,NaHCO3胁迫增加了SOD的活性,CAT,和POD以及抗坏血酸的含量,并启动了谷胱甘肽-S-转移酶途径以去除过量的ROS,但抑制了谷胱甘肽的再生和过氧化物酶的活性。总的来说,中性和碱性盐都抑制红花的光合过程,虽然碱性盐引起的应激水平高于中性盐。红花通过调节其抗氧化系统来减轻应激引起的氧化损伤。
CONCLUSIONS: Compared with NaCl, NaHCO3 caused more serious oxidative damage and photosynthesis inhibition in safflower by down-regulating the expression of related genes. Salt-alkali stress is one of the important factors that limit plant growth. NaCl and sodium bicarbonate (NaHCO3) are neutral and alkaline salts, respectively. This study investigated the physiological characteristics and molecular responses of safflower (Carthamus tinctorius L.) leaves treated with 200 mmol L-1 of NaCl or NaHCO3. The plants treated with NaCl treatment were less effective at inhibiting the growth of safflower, but increased the content of malondialdehyde (MDA) in leaves. Meanwhile, safflower alleviated stress damage by increasing proline (Pro), soluble protein (SP), and soluble sugar (SS). Both fresh weight and dry weight of safflower was severely decreased when it was subjected to NaHCO3 stress, and there was a significant increase in the permeability of cell membranes and the contents of osmotic regulatory substances. An enrichment analysis of the differentially expressed genes (DEGs) using Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes identified significant enrichment of photosynthesis and pathways related to oxidative stress. Furthermore, a weighted gene co-expression network analysis (WGCNA) showed that the darkgreen module had the highest correlation with photosynthesis and oxidative stress traits. Large numbers of transcription factors, primarily from the MYB, GRAS, WRKY, and C2H2 families, were predicted from the genes within the darkgreen module. An analysis of physiological indicators and DEGs, it was found that under saline-alkali stress, genes related to chlorophyll synthesis enzymes were downregulated, while those related to degradation were upregulated, resulting in inhibited chlorophyll biosynthesis and decreased chlorophyll content. Additionally, NaCl and NaHCO3 stress downregulated the expression of genes related to the Calvin cycle, photosynthetic antenna proteins, and the activity of photosynthetic reaction centers to varying degrees, hindering the photosynthetic electron transfer process, suppressing photosynthesis, with NaHCO3 stress causing more pronounced adverse effects. In terms of oxidative stress, the level of reactive oxygen species (ROS) did not change significantly under the NaCl treatment, but the contents of hydrogen peroxide and the rate of production of superoxide anions increased significantly under NaHCO3 stress. In addition, treatment with NaCl upregulated the levels of expression of the key genes for superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), the ascorbate-glutathione cycle, and the thioredoxin-peroxiredoxin pathway, and increased the activity of these enzymes, thus, reducing oxidative damage. Similarly, NaHCO3 stress increased the activities of SOD, CAT, and POD and the content of ascorbic acid and initiated the glutathione-S-transferase pathway to remove excess ROS but suppressed the regeneration of glutathione and the activity of peroxiredoxin. Overall, both neutral and alkaline salts inhibited the photosynthetic process of safflower, although alkaline salt caused a higher level of stress than neutral salt. Safflower alleviated the oxidative damage induced by stress by regulating its antioxidant system.