Two papers describe the genetic basis of long-term heat tolerance in the model plant Arabidopsis thaliana , with implications for crop breeding. Teruaki Taji and colleagues evaluated dozens of lines of the model mustard weed for both long term (37 °C for 36 days) and short term (42°C for 50 minutes) heat stress. The authors found considerable variation within the species, but little overlap between responses to the two different heat challenges, suggesting that long-term heat stress tolerance is controlled by different cellular mechanisms than the more commonly studied short-term heat stress. Chromosomal mapping using the F2 progeny of a cross between a long-term-heat sensitive line and a long-term-heat tolerant line identified a genetic locus responsible for long-term heat tolerance, which the authors name LHT1. This locus is identical to MAC7, in the MOS4-associated complex, a region widely conserved in eukaryotes which encodes a putative RNA helicase involved in mRNA splicing. A single amino acid deletion in a long-term-heat sensitive line caused a loss of function for LHT1, which led to widespread detrimental splicing events. In another paper, Teruaki Taji and a second team of authors also identified mutant plants that are unusually sensitive to long-term heat stress, but not short-term heat stress, which they dub sloh3 and sloh63 . The team found that sloh63 was also hypersensitive to salt stress. The mutations were traced to the same MOS4-associated complex. In addition, both mutants showed abnormal mRNA splicing events and endoplasmic reticulum stress with subsequent unfolded protein response. Treatment with a splicing inhibitor led to decreased long-term heat tolerance and enhanced endoplasmic reticulum stress. According to the authors, the results suggest that maintenance of precise mRNA splicing by the MOS4-associated complex is crucial for surviving long-term heat.
PNAS Nexus
MOS4-associated complex contributes to proper splicing and suppression of ER stress under long-term heat stress in Arabidopsis AND LHT1/MAC7 contributes to alternative splicing under long-term heat stress and mediates variation in the heat tolerance of Arabidopsis
14-Nov-2023