Transcriptomic Profiling Identifies Candidate Genes Involved in the Salt Tolerance of the Xerophyte Pugionium cornutum

Abstract

The xerophyte Pugionium cornutum adapts to salt stress by accumulating inorganic ions (e.g., Cl − ) for osmotic adjustment and enhancing the activity of antioxidant enzymes, but the associated molecular basis remains unclear. In this study, we first found that P. cornutum could also maintain cell membrane stability due to its prominent ROS-scavenging ability and exhibits efficient carbon assimilation capacity under salt stress. Then, the candidate genes associated with the important physiological traits of the salt tolerance of P. cornutum were identified through transcriptomic analysis. The results showed that after 50 mM NaCl treatment for 6 or 24 h, multiple genes encoding proteins facilitating Cl − accumulation and NO 3 − homeostasis, as well as the transport of other major inorganic osmoticums, were significantly upregulated in roots and shoots, which should be favorable for enhancing osmotic adjustment capacity and maintaining the uptake and transport of nutrient elements; a large number of genes related to ROS-scavenging pathways were also significantly upregulated, which might be beneficial for mitigating salt-induced oxidative damage to the cells. Meanwhile, many genes encoding components of the photosynthetic electron transport pathway and carbon fixation enzymes were significantly upregulated in shoots, possibly resulting in high carbon assimilation efficiency in P. cornutum. Additionally, numerous salt-inducible transcription factor genes that probably regulate the abovementioned processes were found. This work lays a preliminary foundation for clarifying the molecular mechanism underlying the adaptation of xerophytes to harsh environments.

Chloride is beneficial for growth of the xerophyte Pugionium cornutum by enhancing osmotic adjustment capacity under salt and drought stresses

“…Plants use Cl – as a beneficial osmoticum by sequestering the majority into the central vacuole, and this process is currently thought to be mediated by the tonoplast-localized chloride channel CLCg ( White and Broadley, 2001 ; Teakle and Tyerman, 2010 ; Nguyen et al , 2016 ). The transcript levels of PcCLCg in the shoots of P. cornutum are highly up-regulated under treatment with 50 mM NaCl ( Cui et al , 2019 ), and hence the sequestration of Cl – into the cell vacuole to enhance OA is a vital strategy for P. cornutum plants growing under saline conditions. In saline environments, the shoot Cl – content in most crop species unavoidably accumulates to extremely high levels, and this particularly restricts the productivity of many crop species, such as soybean and perennial woody species ( Li et al , 2017 ).…”

“…6E , Table 2 ), suggesting that Na + and K + both also function in the OA of P. cornutum in response to NaCl. We have recently found that the expression of the tonoplast Na + /H + antiporter gene PcNHX1 , which encodes a protein mediating Na + and/or K + transport into vacuoles, is up-regulated in the shoots of P. cornutum under treatment with 50 mM NaCl ( Cui et al , 2019 ), and hence the vacuolar compartmentalization of Na + and/or K + may also be vital to its salt tolerance. The transport of Na + and K + into the vacuole is coupled with an increased influx of anionic solutes such as NO 3 – , Cl – , and malate to enhance the OA capacity and to balance the positive electrical charge in the vacuole ( Munns and Tester, 2008 ; Shabala and Shabala, 2011 ; Franco-Navarro et al , 2016 ).…”

“…The nitrate transporter NRT1.5/NPF7.3 has been shown to be an important protein that mediates root-to-shoot transport of NO 3 – in plants ( Lin et al , 2008 ). In Arabidopsis, the expression of AtNRT1.5 / AtNPF7.3 in the roots is down-regulated in response to NaCl treatment ( Chen et al , 2012 ); however, the expression of PcNRT1.5 / PcNPF7.3 in the roots of P. cornutum is maintained at a constant level under 50 mM NaCl treatment ( Cui et al , 2019 ). Therefore, the enhanced ability for long-distance transport of NO 3 – mediated by NRT1.5/NPF7.3 may be another important trait in the salt tolerance of P. cornutum .…”

Physiological and Transcriptional Analyses Provide Insight Into Maintaining Ion Homeostasis of Sweet Sorghum Under Salt Stress

“…As the expression of transcription factors genes (TFs) changes rapidly in response to abiotic stresses [23], we analyzed differentially expressed TFs in tissues of sweet sorghum after salt treatment for 6 h. As shown in Figure 8A, 216 upregulated TFs and 72 downregulated TFs were identified in roots, and these DEGs were categorized into WRKY, MYB, NAC, bHLH, AP2/ERF, bZIP, MADS-box, HSF, ZF, GRAS families. In leaf sheaths and leaf blades, the number of differentially expressed TFs was less than in roots (Figure 8B and C).…”

Quercus suber Roots Activate Antioxidant and Membrane Protective Processes in Response to High Salinity

“…Several transcription factors (TFs) were also found to be involved in abiotic stress responses. For instance, APETALA2/Ethylene-responsive factor (e.g., RAV1 and ERF1) and zinc finger CCCH domain-containing proteins (e.g., CZF1) are induced by saline stress increasing plant tolerance and adaptation [9][10][11][12][13]. Besides TFs, other proteins encoded by stress-responsive genes, such as dehydrins (e.g., LTI30), play a pivotal role in plant defence interacting with membranes phospholipids, proteins, and DNA, thereby protecting them from damage.…”