The transcription factor bZIP60 links the Unfolded Protein Response (UPR) to the Heat Stress Response (HSR) in maize

This was a comparative transcriptome analysis by using high throughput sequencing. To assess the effects of heat stress on maize we used a controlled environment facility called the Enviratron to simulate field conditions. For our experiments, maize plants were subjected to conditions simulating normal diurnal rhythms of light and temperature, with increasing maximal daily temperature (MDT). Maize plants were grown continuously under four different temperature regimes with simulated morning temperatures ramped up over 6 hr to the MDT of 31°C, 33°C, 35°C or 37°C and simulated evening/night time temperatures ramped down over 8 hr to 10°C below the MDT. We tracked the gene expression events of maize W22 seedlings grow under different temperatures (MDT of 31°C, 33°C, 35°C or 37°C) to evaluate how different MDTs affect the program of gene expression in maize. At the same time, we analyzed the effects of temperature on gene expression in bzip60-2 and W22 V4 plants (20 DAG) and V5 plants (27 DAG) in the Enviratron as the temperature reached its MDT to investigate whether and how bZIP60 confers heat stress tolerance in maize. RNA was extracted from small strips of leaf lamina excised from the first fully expanded leaf of V4 and V5 W22 plants (at 20 and 27 DAG, respectively). Plants were sampled in triplicates. Each sample was collected in 3 biological replicates, and each replicate from mutiple plants under the same condition.