Transcriptome dynamics of daily, seasonal and annual cycles in the needles of Douglas-fir (Pseudotsuga menziesii Mirb.)

Rhythms of light, temperature, and precipitation provide signals that regulate rhythmic gene expression and growth in trees. To understand the relationship between seasonal rhythms and seasonal gene expression responses in conifers, we examined diurnal, seasonal, and circannual needle mRNA accumulation in Douglas-fir, Pseudotsuga menziesii. Using mRNA sequencing, we sampled 101 bp reads from 19 trees and constructed a combined 'pan-transcriptome' reference that includes 199,471 transcripts (PRJNA356432). Using this reference, we mapped RNA-seq reads from samples that capture diurnal variation between two families of trees (12 time points; PRJNA263611), seasonal variation between three families of trees (PRJNA188506), and annual variation between two families of trees (16 time points; PRJNA243096). This study shows that thousands of genes reach peak annual activity during the winter and summer solstices, and that photoperiod and light quality is a dominant driver of daily and annual transcription in Douglas-fir.

光照、温度与降水的节律为树木的节律性基因表达及生长提供调控信号。为揭示针叶树季节节律与季节基因表达响应之间的关联，我们对花旗松（*Pseudotsuga menziesii*）针叶的日间、季节及年周期mRNA积累量开展了检测。本研究通过mRNA测序技术，从19棵花旗松中获取了101 bp的测序读段，并构建了包含199471条转录本的整合型“泛转录组（pan-transcriptome）”参考序列（BioProject编号：PRJNA356432）。依托该参考序列，我们对三类样本的RNA测序读段进行了比对分析：其一为捕获两个树木家系日间表达差异的样本（含12个时间点，BioProject编号：PRJNA263611）；其二为捕获三个树木家系季节表达差异的样本（BioProject编号：PRJNA188506）；其三为捕获两个树木家系年周期表达差异的样本（含16个时间点，BioProject编号：PRJNA243096）。本研究表明，数千个基因在冬至与夏至时达到年度表达活性峰值，且光周期与光质是调控花旗松日间及年度转录水平的核心驱动因子。