Mutations in an Arabidopsis Mitochondrial Transcription Termination Factor–Related Protein Enhance Thermotolerance in the Absence of the Major Molecular Chaperone HSP101

Abstract

The molecular chaperone heat shock protein101 (HSP101) is required for acquired thermotolerance in plants and other organisms. To identify factors that interact with HSP101 or that are involved in thermotolerance, we screened for extragenic suppressors of a dominant-negative allele of Arabidopsis thaliana HSP101, hot1-4. One suppressor, shot1 (for suppressor of hot1-4 1), encodes a mitochondrial transcription termination factor (mTERF)-related protein, one of 35 Arabidopsis mTERFs about which there is limited functional data. Missense (shot1-1) and T-DNA insertion (shot1-2) mutants suppress the hot1-4 heat-hypersensitive phenotype. Furthermore, shot1-2 suppresses other heat-sensitive mutants, and shot1-2 alone is more heat tolerant than the wild type. SHOT1 resides in mitochondria, indicating it functions independently of cytosolic/nuclear HSP101. Microarray analysis suggests altered mitochondrial function and/or retrograde signaling in shot1-2 increases transcripts of other HSPs and alters expression of redox-related genes. Reduced oxidative damage is the likely cause of shot1 thermotolerance, indicating HSP101 repairs protein oxidative damage and/or reduced oxidative damage allows recovery in the absence of HSP101. Changes in organelle-encoded transcripts in shot1 demonstrate that SHOT1 is involved in organelle gene regulation. The heat tolerance of shot1 emphasizes the importance of mitochondria in stress tolerance, and defining its function may provide insights into control of oxidative damage for engineering stress-resistant plants.

Overexpression of receptor-like kinase ERECTA improves thermotolerance in rice and tomato

“…Plants respond to temperature changes by reprogramming their growth and development [4][5][6][7][8] , and progress has been made towards genetic modification of plants to increase their tolerance to heat stress. However, these studies have mainly been restricted to the model plant Arabidopsis [9][10][11][12][13][14] . Many studies have shown that expression of heat shock proteins (HSPs) can improve the tolerance of transgenic plants to heat shock (short exposure to high temperatures) 15 .…”

ClpB/Hsp100 proteins and heat stress tolerance in plants

“…The ClpB subfamily is characteristically induced by HS and is different from other Clp members in this respect. As plant ClpBs have a molecular weight of approximately 100 kDa and HS inducible expression, they are also referred to as Hsp100 proteins (Kim et al, 2012;. We will restrict our discussion to only ClpB/Hsp100 proteins for the remainder of this review.…”

Antioxidant Enzymes

“…Microarray analysis revealed that expression of HSPs and redox-related genes increased in shot1-2 through retrograde signaling. Further evidence suggested that HSP101 may repair proteins damaged by oxidative stress (Kim et al, 2012).…”