Adaptation to low temperatures in the wild tomato species Solanum chilense

Abstract

Molecular adaptation to abiotic stresses in plants is a complex process based mainly on the modifications of gene transcriptional activity and the alteration of protein-protein interactions. We used a combination of population genetic, comparative transcriptomic and plant physiology approaches to investigate the mechanisms of adaptation to low temperatures in Solanum chilense populations distributed along Andean altitudinal gradients. We found that plants from all populations have high chilling tolerance, which does not correlate with temperatures in their native habitats. In contrast, tolerance to freezing shows a significant association with altitude and temperature variables. We also observed the differences in expression patterns of cold-response genes between plants from high- and low-altitude populations. These results suggest that genetic adaptations to low temperatures evolved in high-altitude populations of S. chilense. At the transcriptional level, these adaptations may include high levels of constitutive expression of the genes encoding ICE1, the key transcription factor of the cold signalling pathway, and chloroplast ω-3 fatty acid desaturase FAD7. At the sequence level, a signature of selection associated with the adaptation to high altitudes was detected at the C-terminal part of ICE1 encoding the ACT regulatory domain.

The wild tomato speciesSolanum chilenseshows variation in pathogen resistance between geographically distinct populations

“…These populations experience considerable variation in geographic parameters like precipitation and temperatures. It is known that S. chilense has a clear demographic pattern and signs of adaptations to climatic differences between different populations (Fischer et al, 2011; Fischer et al, 2013; Nosenko et al, 2016). A demographic pattern of North–South colonisation is observable with larger and more diverse populations in the north of the range and smaller and less diverse populations in the south.…”

“…In addition, S. chilense shows clear climatic adaptations. Populations from drier regions are responding faster to drought (Fischer et al, 2013) and individual populations found at high altitudes (>3,000 m) show higher freezing tolerance (Nosenko et al, 2016)  S. chilense has also been the source of resistance loci against the fungus Verticilium dahliae (Tabaeizadeh et al, 1999) and against various viruses (Griffiths & Scott, 2001; Ji et al, 2007; Verlaan et al, 2013). Seeing that S. chilense occurs in such a wide range of habitats and that the species shows specific signs of local climatic adaptations, we wondered whether we could find variation for pathogen resistance as well.…”

Subsets of NLR genes show differential signatures of adaptation during colonization of new habitats

“…Solanum chilense occurs in southern Peru and northern Chile. Local adaptation to abiotic and biotic stresses in S. chilense or its sister species is indicated, first, by signatures of positive selection in genes involved in cold-and drought-stress response (Xia et al, 2010;Fischer et al, 2013;Nosenko et al, 2016;B€ ondel et al, 2018), second, by balancing selection in several genes of the Pto resistance pathway providing resistance to Pseudomonas sp. (Rose et al, 2011), and, third, by variable resistant phenotypes against filamentous pathogens across populations .…”

Insights into the regulation of C‐repeat binding factors in plant cold signaling

“…The function of ICE1 is conserved in many plant species, and the heterogeneous expression of the rice, maize, or tomato ICE1 orthologs in Arabidopsis enhanced plant freezing tolerance (Nosenko et al ; Deng et al ; Lu et al ). ICE2, a paralog of ICE1, is also involved in regulating CBF expression and freezing tolerance (Fursova et al ).…”