Vitis 60, 143–151 (2021) © The author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution Share-Alike License (https://creativecommons.org/licenses/by/4.0/). DOI: 10.5073/vitis.2021.60.143-151 Correspondence to: Dr. A. Upadhyay , ICAR-National Research Centre for Grapes, Manjari Farm Post, Solapur Road, Pune – 412307, Maharashtra, India. E-mail: Anuradha.upadhyay@icar.gov.in Global transcriptome analysis of heat stress response of grape variety 'Fantasy Seedless' under diferent irrigation regimens A. Upadhyay and A. K. Upadhyay ICAR-National Research Centre for Grapes, Manjari Farm Post, Pune, Maharashtra, India Summary Grapevine (Vitis vinifera L.), a commercially im- portant fruit crop worldwide, faces several challenging conditions during its growth cycle. Among many abiotic stresses, heat and moisture stresses have major impact on grapevine productivity and fruit quality. Transcriptome analysis of heat stress response of grape variety 'Fanta- sy Seedless' grown under diferent irrigation regimens identifed large number of diferentially expressed genes. Genes belonging to chaperone mediated protein folding and cell-wall modifcation pathways were found to play a signifcant role in plant response to heat as well as moisture stress. Subsurface irrigation helped minimize the adverse efects of stress through modulation of genes involved in cell homeostasis. The study has given critical insight into grapevine response to heat stress arising due to aberrant weather conditions. Key words: grape; heat stress response; protein folding; cell homeostasis. Introduction Grape (Vitis vinifera L.) is one of the most important fruit crop globally. It is cultivated over an area of 7,157,658 ha (FAOSTAT 2008) under diferent climatic conditions. During its growth cycle, grapevine experiences many biotic and abiotic stresses. Heat stress is one of the major abiotic stresses afecting grape production and quality. Heat stress is defned as the occurrence of temperature above the optimum. In grape, temperatures above 35 °C results in reduced photosynthesis in leaves (Kriedemann 1968). The breakdown of cellular organization due to high temper- atures leads to cell injury or even cell death (Wahid et al. 2007). Injuries due to heat includes protein denaturation and aggregation, enzyme inactivatin, loss of membrane integ- rity resulting in generation of reactive oxygen species and other toxic compounds and causing metabolic imbalance. In many grape growing regions, the day temperature rises above 40 °C which afects grapevine phenology, resulting in altered growth pattern and afecting grape quality (Greer and Weedon 2013, Abeysinghe et al. 2019). In grape, several researchers have studied the physiological changes like net photosynthesis, hormone changes, cell signaling etc. (Wang et al. 2009, Luo et al. 2011, Greer and Weedon 2013), grapevine performance (Greer and Weedon 2013) and quality (Mori et al. 2007) in response to heat stress. In recent years, transcriptome analysis has given much insight into molecular mechanism of heat stress response in grape. Liu et al. (2012) reported association of heat stress and re- covery with multiple processes and mechanisms including stress-related genes, transcription factors, and metabolism. Transcriptome analysis of berries under different high temperatures revealed induction of HSP proteins, which probably facilitate berry ripening through stabilization of protein functions and transmembrane transporter density (Carbonell-Bejerano et al. 2013). Rienth et al. (2014) observed diferences in heat stress responsive pathways according to day or night treatment especially for genes involved in acidity and phenylpropanoid metabolism. The high rate of evaporation under elevated ambient temperature conditions leads to reduced soil moisture and subsequent moisture stress to the grapevine. Grapevine is considered moderately tolerant to moisture stress and is well adapted to semi-arid climate (Chaves et al. 2010). The water defcit is often used to enhance aroma and improve berry composition of wine grapes. However, in table grapes, defcit irrigation at critical stages of growth adversely afects berry size and quality as well as yield (Zúñiga-Espinoza et al. 2015, Permanhani et al. 2016). The extent of adverse efect depends on soil type, time of stress and climate during grow- ing season besides cultivar and rootstock type (Cardone et al. 2019). Physiological response of grapevine to water defcit stress has been studied in detail and comprehensively reviewed by Chaves et al. (2010). Transcriptome analysis of water stress revealed cultivar specifc modulation of genes in response to water stress (Catacchio et al. 2019) and con- sisting of a multi-step component system involving several genes regulating various pathways (Cramer et al. 2007, Haider et al. 2017). Under feld conditions, a variety of abiotic stresses like heat, water, salinity and oxidative stress occur simultaneously. Plants use a diversity of mechanisms and combinations of mechanisms to tolerate each of these stresses (Roy et al. 2011). The combined efect of heat and drought is higher than the individual stress and elicit diferent response as compared to the individual stress (Grigorova et al. 2011). In grape, several researchers have studied grape- vine response to drought, salinity and co-occurring stresses (Cramer et al. 2007, Chaves et al. 2010, Cramer 2010, Ro- cheta et al. 2014) at transcript level. Increased temperatures