Deciphering Drought-Response in Wheat (Triticum aestivum): Physiological, Biochemical, and Transcriptomic Insights into Tolerant and Sensitive Cultivars under Dehydration Shock

Birsen Cevher-Keskin^1*Yasemin Yildizhan¹A.Hediye Sekmen²Rumeysa Fayetorbay³Osman Uğur Sezerman³Buğra Özer⁴Selma Onarıcı^5,6İsmail Türkan^7,8Mahmut Tör^9*

• ¹TUBITAK, Marmara Research Center, Life Sciences, Kocaeli, Türkiye
• ²Ege Universitesi Biyoloji Bolumu, Izmir, Türkiye
• ³Acibadem Universitesi, Istanbul, Türkiye
• ⁴Sabanci Universitesi Muhendislik ve Doga Bilimleri Fakultesi, Istanbul, Türkiye
• ⁵Tubitak Marmara Arastirma Merkezi, Gebze, Türkiye
• ⁶Bozok Universitesi Tip Fakultesi, Yozgat, Türkiye
• ⁷Ege Universitesi, Izmir, Türkiye
• ⁸Yasar Universitesi, Izmir, Türkiye
• ⁹University of Worcester, Worcester, United Kingdom

Introduction: Wheat (Triticum aestivum L.) is a major staple crop, but its productivity is severely threatened by drought, especially during reproductive stages. Climate change and water overexploitation intensify this challenge, with yield losses of up to 80% in arid regions and projected global declines of ~29%. Drought tolerance is complex, involving physiological, biochemical, and molecular mechanisms, including stomatal regulation, osmolyte accumulation, and stress-responsive genes. Advances in transcriptomics, functional genomics, and genome editing have identified key regulators (DREB, ERF, SnRK2), antioxidant enzymes, and ABA signalling components as targets for improving drought resilience, making development of tolerant varieties a priority. Materials and Methods: This study investigates transcriptomic responses in root and leaf tissues of three wheat cultivars, Atay 85 (drought-sensitive), Gerek 79, and Müfitbey (drought-tolerant), subjected to 4- and 8-hour shock-dehydration stress. Biochemical assays assessed oxidative damage (TBARS) and antioxidant enzyme activities prior to RNAseq. Differential gene expression analysis identified highly expressed genes, including TaZFP36, TaMC5, TaGI, TaGLP9-1, and TaFER, for RNAseq validation in both tissues of tolerant and sensitive cultivars. Results: Transcriptomic analysis revealed distinct metabolic strategies. Photosynthesis-related processes were broadly downregulated, while extracellular and membrane components were upregulated, reflecting stress defence. Atay 85 exhibited severe metabolic suppression and ATP depletion, Gerek 79 conserved energy by suppressing photosynthesis while enhancing osmoprotective sugar metabolism and lignin/flavonoid biosynthesis, and Müfitbey integrated metabolic dormancy, hormonal signalling, and antioxidant defence, with stable CAT and elevated SOD activity mitigating oxidative damage. Roots prioritized metabolic adjustments for stress reduction and developmental adaptation, whereas leaves focused on maintaining photosynthesis and limiting protein damage. Functional enrichment indicated upregulation of ABA-mediated signalling, protein binding, and cellular metabolic processes in tolerant cultivars. Discussion: This study highlights cultivar-specific molecular and biochemical strategies underlying drought tolerance, emphasizing key candidate genes and antioxidant mechanisms. The distinct metabolic strategies underscore the importance of tailored molecular mechanisms to guide breeding for wheat resilience under water-limited conditions.