Jeroni Galmes

1 Introduction Drought stress is a major agricultural challenge, increasingly worsened by climate change (Gupta et al. 2020). Rising global temperatures and unpredictable rainfall patterns are making droughts more frequent and severe, threatening crop yields and food security (Muluneh 2021). The Mediterranean basin is warming 20% faster than the global average (UNEP 2021; COP29 2024).

INTRODUCTION A vast expanse of the Earth's surface is characterized by harsh conditions, including extreme temperatures, high and low pH levels, high salinity, high incident radiation, nutrient limitation, and drought (Rampelotto, 2013). Only a select group of organisms, known as extremophiles, developed specific adaptations to thrive in these environments (Morgan-Kiss et al., 2006; Reed et al., 2013). Thermophiles require growth temperatures above 45°C and psychrophiles below 15°C.

Introduction Rubisco (d-ribulose 1,5-bisphosphate carboxylase/oxygenase) is the fundamental link between inorganic and organic matter on Earth. It controls the global carbon cycle by catalysing the first step in the Calvin–Benson–Bassham cycle, fixing CO2 into ribulose 1,5-bisphosphate (RuBP) and producing two molecules of 3-phosphoglycerate (3-PGA). Despite this pivotal role, Rubisco is unable to fully discriminate between CO2 and its competing substrate, O2.