Chao Wun S, Doğramaci Münevver, Anderson James V, Foley Michael E, Horvath David P
USDA-Agricultural Research Service, Biosciences Research Lab, Sunflower and Plant Biology Research Unit, 1605 Albrecht Boulevard N, Fargo 58102, ND, USA.
BMC Plant Biol. 2014 Aug 12;14:216. doi: 10.1186/s12870-014-0216-4.
Leafy spurge (Euphorbia esula L.) is a herbaceous perennial weed and dormancy in both buds and seeds is an important survival mechanism. Bud dormancy in leafy spurge exhibits three well-defined phases of para-, endo- and ecodormancy; however, seed dormancy for leafy spurge is classified as physiological dormancy that requires after-ripening and alternating temperature for maximal germination. Overlaps in transcriptome profiles between different phases of bud and seed dormancy have not been determined. Thus, we compared various phases of dormancy between seeds and buds to identify common genes and molecular processes, which should provide new insights about common regulators of dormancy.
Cluster analysis of expression profiles for 201 selected genes indicated bud and seed samples clustered separately. Direct comparisons between buds and seeds are additionally complicated since seeds incubated at a constant temperature of 20°C for 21 days (21d C) could be considered paradormant (Para) because seeds may be inhibited by endosperm-generated signals, or ecodormant (Eco) because seeds germinate after being subjected to alternating temperature of 20:30°C. Since direct comparisons in gene expression between buds and seeds were problematic, we instead examined commonalities in differentially-expressed genes associated with different phases of dormancy. Comparison between buds and seeds ('Para to Endo buds' and '21d C to 1d C seeds'), using endodormant buds (Endo) and dormant seeds (1d C) as common baselines, identified transcripts associated with cell cycle (HisH4), stress response/transcription factors (ICE2, ERFB4/ABR1), ABA and auxin response (ABA1, ARF1, IAA7, TFL1), carbohydrate/protein degradation (GAPDH_1), and transport (ABCB2). Comparison of transcript abundance for the 'Eco to Endo buds' and '21d C to 1d C seeds' identified transcripts associated with ABA response (ATEM6), auxin response (ARF1), and cell cycle (HisH4). These results indicate that the physiological state of 21d C seeds is more analogous to paradormant buds than that of ecodormant buds.
Combined results indicate that common molecular mechanisms associated with dormancy transitions of buds and seeds involve processes associated with ABA and auxin signaling and transport, cell cycle, and AP2/ERF transcription factors or their up-stream regulators.
叶状大戟（Euphorbia esula L.）是一种多年生草本杂草，芽和种子的休眠是重要的生存机制。叶状大戟的芽休眠表现出明显的三个阶段：预休眠、内休眠和生态休眠；然而，叶状大戟的种子休眠被归类为生理休眠，需要经过后熟和变温处理才能达到最大发芽率。芽休眠和种子休眠不同阶段的转录组图谱重叠情况尚未确定。因此，我们比较了种子和芽休眠的不同阶段，以确定共同的基因和分子过程，这将为休眠的共同调节因子提供新的见解。
对201个选定基因表达谱的聚类分析表明，芽和种子样本分别聚类。芽和种子之间的直接比较更加复杂，因为在20°C恒温下培养21天（21d C）后的种子可能被认为处于预休眠状态（Para）——因为种子可能受到胚乳产生的信号抑制，或者处于生态休眠状态（Eco）——因为种子在经历20:30°C的变温后发芽了。由于芽和种子之间基因表达的直接比较存在问题，我们转而研究与不同休眠阶段相关的差异表达基因的共性。以内休眠芽（Endo）和休眠种子（1d C）作为共同基线进行芽和种子之间（“预休眠到内休眠芽”和“21d C到1d C种子”）的比较，确定了与细胞周期（HisH4）、应激反应/转录因子（ICE2、ERFB4/ABR1）、脱落酸和生长素反应（ABA1、ARF1、IAA7、TFL1）、碳水化合物/蛋白质降解（GAPDH_1）和转运（ABCB2）相关的转录本。“生态休眠到内休眠芽”和“21d C到1d C种子”转录本丰度的比较确定了与脱落酸反应（ATEM6）、生长素反应（ARF1）和细胞周期（HisH4）相关的转录本。这些结果表明21d C种子的生理状态与预休眠芽比生态休眠芽更为相似
综合结果表明芽和种子休眠转变相关的共同分子机制涉及与脱落酸和生长素信号传导及转运、细胞周期以及AP2/ERF转录因子或其上游调节因子相关的过程。
