Lessons from the Khejri: A desert tree’s small heat shock protein as a tool for engineering heat tolerance

Rising global temperatures and the increasing frequency of heat extremes threaten crop productivity worldwide, making the discovery of naturally evolved thermotolerance determinants an urgent priority. Plants native to hot, arid regions are a valuable genetic resource, having evolved to sustain growth under conditions that are lethal to most crops. Prosopis cineraria (khejri), the state tree of Rajasthan, India, thrives in the Thar Desert, where temperatures can exceed 50°C, and is therefore an excellent source of heat-adaptive genes. Characterizing the proteins that underpin this natural resilience offers a direct route to transferring desert-derived stress tolerance to crop species. Small heat shock proteins (sHSPs) are ATP-independent molecular chaperones that protect cellular proteins from heat-induced aggregation and play a central role in thermotolerance. In the present study, we focused on PcHSP22.7, a cytosolic sHSP from P. cineraria, to examine its potential for improving heat tolerance in heterologous systems. Because sHSPs act as the first line of cellular defence against protein damage, understanding their functional behaviour in different hosts is essential for their rational deployment in biotechnology. PcHSP22.7 was introduced into multiple expression systems, including the bacterium Escherichia coli, the methylotrophic yeast Pichia pastoris and plant systems, and work in tomato is currently in progress. Expression of the recombinant protein was confirmed by SDS-PAGE. Expression of PcHSP22.7 enhanced the survival of both E. coli and P. pastoris under high-temperature conditions, demonstrating that this desert-tree protein confers protection against heat stress in evolutionarily distant hosts. The protective effect across bacterial and eukaryotic microbial systems points to a chaperone function that operates independently of host-specific factors, which supports its broader applicability. Successful expression in these diverse hosts also provides a solid platform for further functional and mechanistic studies of this protein. Building on these findings, current work extends the investigation to tomato, an economically important crop that is highly sensitive to heat stress, with the aim of evaluating the translational potential of PcHSP22.7 for crop improvement. Together, these studies position PcHSP22.7 as a promising genetic resource for engineering thermotolerance and illustrate how proteins from plants adapted to extreme environments can inform strategies for developing climate-resilient crops. Rising global temperatures and the increasing frequency of heat extremes threaten crop productivity worldwide, making the discovery of naturally evolved thermotolerance determinants an urgent priority. Plants native to hot, arid regions are a valuable genetic resource, having evolved to sustain growth under conditions that are lethal to most crops. Prosopis cineraria (khejri), the state tree of Rajasthan, India, thrives in the Thar Desert, where temperatures can exceed 50°C, and is therefore an excellent source of heat-adaptive genes. Characterizing the proteins that underpin this natural resilience offers a direct route to transferring desert-derived stress tolerance to crop species. Small heat shock proteins (sHSPs) are ATP-independent molecular chaperones that protect cellular proteins from heat-induced aggregation and play a central role in thermotolerance. In the present study, we focused on PcHSP22.7, a cytosolic sHSP from P. cineraria, to examine its potential for improving heat tolerance in heterologous systems. Because sHSPs act as the first line of cellular defence against protein damage, understanding their functional behaviour in different hosts is essential for their rational deployment in biotechnology. PcHSP22.7 was introduced into multiple expression systems, including the bacterium Escherichia coli, the methylotrophic yeast Pichia pastoris and plant systems, and work in tomato is currently in progress. Expression of the recombinant protein was confirmed by SDS-PAGE. Expression of PcHSP22.7 enhanced the survival of both E. coli and P. pastoris under high-temperature conditions, demonstrating that this desert-tree protein confers protection against heat stress in evolutionarily distant hosts. The protective effect across bacterial and eukaryotic microbial systems points to a chaperone function that operates independently of host-specific factors, which supports its broader applicability. Successful expression in these diverse hosts also provides a solid platform for further functional and mechanistic studies of this protein. Building on these findings, current work extends the investigation to tomato, an economically important crop that is highly sensitive to heat stress, with the aim of evaluating the translational potential of PcHSP22.7 for crop improvement. Together, these studies position PcHSP22.7 as a promising genetic resource for engineering thermotolerance and illustrate how proteins from plants adapted to extreme environments can inform strategies for developing climate-resilient crops.