Transcriptomic analysis of Col plants and wrky48 mutants subjected to high light, heat stress and their combination

Plants growing in the field are subjected to high light intensities that are often accompanied by high temperatures. In this work, we analyzed transcriptomic responses of wild type Col plants and mutants defective in the transcription factor WRKY48 to understand why wrky48 mutants are more tolerant to the combination of high temperatures and high light stress. Our results indicate that jasmonic acid accumulation induced by the combination of high light and heat stress could repress WRKY48 expression, enabling the expression of acclimation genes to this stress combination. Arabidopsis thaliana wild-type Col-0 (var Columbia-0) and homozygous knockout mutants (Col-0 background) wrky48-1 (Salk_066438C) were grown in peat pellets (Jiffy-7; http://www.jiffygroup.com/) at 23°C under long-day growth conditions (12-h light from 7 AM to 7 PM; 50 μmol m−2 s−1/12-h dark from 7 PM to 7 AM). Individual high light stress (HL) and heat stress (HS), and combined HL and HS (HL+HS) were applied in parallel using 30-day-old Arabidopsis plants (wild-type Col-0 and wrky48-1). HL was applied by exposing plants to 900 µmol m−2 s−1 at 23 °C for 8 h. HS was applied by subjecting plants to 40 °C, 50 µmol m−2 s−1, for 8 h. HL+HS was performed by simultaneously subjecting plants to 900 µmol m−2 s−1 of light stress and 40°C for 8 h. Control (CT) plants were maintained at 50 µmol m−2 s−1 and 23°C throughout the entire experiment. All experiments were conducted during the light cycle, from 9 A.M. to 5 P.M., and were repeated at least three times with 45 plants per stress treatment and biological repeat. True leaves pooled from at least 20 different plants subjected to each of the control and stress treatments were used for each biological repeat for RNAseq analysis, and three biological repeats were performed. Total RNA was isolated using RNeasy plant mini kit (Qiagen) according to the manufacturer's instructions. RNA libraries for sequencing were prepared using standard Illumina protocols and RNA sequencing was performed using NovaSeq 6000 by Novogene co. Ltd (Cambridge, UK).