1RNA-Seq is a whole-transcriptome analysis method used to research biological mechanisms 2 2 3 1 low-cost and easy RNA-Seq (Lasy-Seq), and used it to investigate temperature responses in 3 2 Arabidopsis thaliana. We analysed how sub-ambient temperatures (10-30°C) affected the 3 3 plant transcriptomes, using time-courses of RNA-Seq from plants grown in randomly 3 4 fluctuating temperature conditions. Our results suggest that there are diverse mechanisms 3 5 behind plant temperature responses at different time scales. 3 6 3 7 3 8 3 9RNA-Seq enables us to analyse transcriptomes, the comprehensive expression profile of the 4 0 genome, and has been used for a variety of analyses, such as the effects of mutations 1,2 , 4 1 stress responses 3-5 , chemical biosynthesis pathways 6 and plant-pathogen interactions 7,8 . 4 2 However, large scale experiments have been limited due to the large costs required for library 4 3 preparation and sequencing. Recently, with the rise of single cell RNA-Seq technology, an 4 4increasing number of methods for high-throughput RNA-Seq have been reported 9 . In 4 5 conventional RNA-Seq methods, enrichment of mRNA occurs at the first step of library 4 6 preparation, with oligo-dT beads or enzymatic digestion of rRNA in samples 10 . The 4 7 preparation of a large number of libraries is cost-and labour-intensive and can result in high 4 8 variance of the quality and quantity of samples. Previous studies of single cell RNA-Seq have 4 9 7 1 identified 25,26 . Furthermore, several studies have indicated that plants refer to past 7 2temperatures, such as the existence of heat shock memory 27,28 . Moreover, it has also been 7 3reported that sub-lethal heat stress of plants can result in acquired tolerance to subsequent 7 4 higher heat stress events, known as heat acclimation. Heat stress memories are stored for 7 5 longer intervals, this is different from acute tolerance known as a heat shock response 29-31 .
6Because majority of these previous studies were conducted under a few constant-temperature 7 7 conditions, less is known about how long or how much plants refer past temperature.
8In this study, we have developed a high-throughput and cost-effective RNA-Seq library 7 9 preparation method with RT indexing of total-RNA samples, which let us skip the process of 8 0 mRNA enrichment and pools all samples into a single tube at an early stage of library 8 1 preparation. Using this method, we have revealed the ambient temperatures and durations of 8 2 exposure to them, by randomly changing the growth temperatures from 10°C to 30°C every 8 3 other day, that affected the transcriptomes of A. thaliana. 8 4 Results 8 5Optimization of RNA-Seq library preparation methods for high-throughput processing 8 6 To develop a high-throughput and cost-effective RNA-Seq preparation method, we applied 8 7 methods used for single cell RNA-Seq (scRNA-Seq) in previous studies. In the scRNA-Seq 8 8 method, the amount of input RNA was small, therefore all samples were pooled after being 8 9indexed by an index-added pri...