Oligogalactolipid production during cold challenge is conserved in early diverging lineages

Abstract

Severe cold, defined as a damaging cold beyond acclimation temperatures, has unique responses, but the signaling and evolution of these responses are not well understood. Production of oligogalactolipids, which is triggered by cytosolic acidification in Arabidopsis (Arabidopsis thaliana), contributes to survival in severe cold. Here, we investigated oligogalactolipid production in species from bryophytes to angiosperms. Production of oligogalactolipids differed within each clade, suggesting multiple evolutionary origins of severe cold tolerance. We also observed greater oligogalactolipid production in control samples instead of temperature-challenged samples of some species. Further examination of representative species revealed a tight association between temperature, damage, and oligogalactolipid production that scaled with the cold tolerance of each species. Based on oligogalactolipid production and transcript changes, multiple angiosperm species share a signal of oligogalactolipid production initially described in Arabidopsis, cytosolic acidification. Together, these data suggest that oligogalactolipid production is a severe cold response that originated from an ancestral damage response that remains in many land plant lineages and that cytosolic acidification may be a common signaling mechanism for its activation.

Exploring cotton SFR2’s conundrum in response to cold stress

“…Soil-grown plants were grown precisely as described previously. 18 Soil-grown plants were incubated at normal day temperatures (22°C) for 3 to 4 weeks before cold acclimation at 4°C with 12-h day/night and 60 μmol m −2 s −1 light for 1 week. Plate grown plants were incubated at normal day temperatures (22°C) with a nighttime temperature of 18°C and 120 μmol m −2 s −1 of light before cold acclimation.…”

“…Arabidopsis cytosolic acidification was completed on excised leaves as described in. 18 Cotton cytosolic acidification was completed on young leaves of vegetative-stage Gossypium raimondii with three or more fully expanded leaves was used for the TGDG accumulation tests. The acid test was completed directly on a fully expanded leaf by using plastic wrap with 20 mM acetic acid at pH 5.7.…”

“… 16 Moreover, cytosolic acidification triggered by low temperatures has been established as a highly conserved step for SFR2 activation in Arabidopsis and other plant species. 7 , 18 …”

“…TGDG accumulation serves as a reliable proxy for SFR2 activity under cold or acid stress. 7 , 18 A recent study comparing TGDG levels across diverse species described cotton, as a fascinating outlier, exhibiting minimal accumulation of TGDG under both normal and cold conditions, despite its close kinship to the highly accumulating model species, Arabidopsis thaliana . Cotton, a vital fiber and oilseed crop, has a myriad of varieties which results in many optimal growing temperatures for the genus.…”

“…Because cotton is cold sensitive an unpredictable frost of 2007 decimated US crops, particularly in the cotton-rich Southeast, and it stands as a stark reminder of our vulnerability to climate instability. 27 Because cotton is a major fiber and oilseed agricultural crop that responds differently than Arabidopsis to low temperatures, 28 and has an unusually poor TGDG accumulation, 18 we decided to focus on its activation of SFR2. We hypothesized that cotton Gr SFR2 would sense low temperatures differently than Arabidopsis At SFR2.…”