Expression of major photosynthetic and salt‐resistance genes in invasive reed lineages grown under elevated CO₂ and temperature

Abstract

It is important to investigate the molecular causes of the variation in ecologically important traits to fully understand phenotypic responses to climate change. In the Mississippi River Delta, two distinct, sympatric invasive lineages of common reed (Phragmites australis) are known to differ in several ecophysiological characteristics and are expected to become more salt resistant due to increasing atmospheric CO2 and temperature. We investigated whether different patterns of gene expression can explain their ecophysiological differences and increased vigor under future climatic conditions. We compared the transcript abundance of photosynthetic genes of the Calvin cycle (Rubisco small subunit, RbcS; Phosphoglycerate kinase, PGK; Phosphoribulokinase, PRK), genes related with salt transport (Na+/H+ antiporter, PhaNHA) and oxidative stress response genes (Manganese Superoxide dismutase, MnSOD; Glutathione peroxidase, GPX), and the total aboveground biomass production between two genotypes representing the two lineages. The two genotypes (Delta-type, Mediterranean lineage, and EU-type, Eurasian lineage) were grown under an ambient and a future climate scenario with simultaneously elevated CO2 and temperature, and under two different soil salinities (0‰ or 20‰). We found neither differences in the aboveground biomass production nor the transcript abundances of the two genotypes, but soil salinity significantly affected all the investigated parameters, often interacting with the climatic conditions. At 20‰ salinity, most genes were higher expressed in the future than in the ambient climatic conditions. Higher transcription of the genes suggests higher abundance of the protein they code for, and consequently increased photosynthate production, improved stress responses, and salt exclusion. Therefore, the higher expression of these genes most likely contributed to the significantly ameliorated salinity impact on the aboveground biomass production of both P. australis genotypes under elevated temperature and CO2. Although transcript abundances did not explain differences between the lineages, they correlated with the increased vigor of both lineages under anticipated future climatic conditions.

Using Transcriptomics to Identify Differential Gene Expression in Response to Salinity among Australian Phragmites australis Clones

“…However, in our study the expression levels of many of the genes commonly associated with a response to salt stress in plants were not significantly different in P. australis clones irrigated with saline compared to fresh water ( Table 3 ). These genes included those previously identified as varying between salt tolerant and salt sensitive plants of P. australis ( Zhao et al, 2004 ; Takahashi et al, 2007a , b , c , 2009 ; Eller et al, 2014 ) and in other species (e.g., Munns and Tester, 2008 ) including the HAK/HKT gene family. Several genes that have previously been linked to salt stress in other plant species were significantly down-regulated, or the expression did not differ between P. australis plants exposed to saline water compared to fresh water while we had predicted significant up-regulation.…”

“…In addition, P. australis can reproduce both sexually and asexually further contributing to its success in establishing and persisting under a range of environmental conditions. However, its local abundance is affected by several environmental factors including variable levels of nutrients, water and salinity, niche availability and its genetic make-up ( Eller et al, 2014 ). For example, Achenbach et al (2013) found substantial differences in salt tolerance between clones of P. australis supporting the idea that varied clonal responses have a genetic basis.…”

De novo transcriptome assembly and analysis of Phragmites karka, an invasive halophyte, to study the mechanism of salinity stress tolerance

“…Phragmites is a halophyte grass belonging to the family Poaceae and found in both fresh and saline wetland systems, as well as brackish waters such as river banks and lake shores. Four species of Phragmites are found worldwide, namely, Phragmites australis, P. japonicus, P. karka, and P. mauritianus 1 . Phragmites australis, the most widespread species, is genetically complex with a range of ploidy levels including 2n = 3×, 4×, 8×, 12× 2 .…”

Comparative Proteomic Analysis of Two Manilkara Species Leaves Under NaCl Stress

“…Expression of major photosynthetic and salt-resistance genes in invasive reed lineages grown under elevated CO2 and temperature showed that at 20‰ salinity, most genes were higher expressed in the future than in the ambient climatic conditions. However, the expression of PGK was not negatively affected by the salt treatment (25).…”