Maize is a subtropical, cold-sensitive species. However, some varieties of this species have the potential to withstand long-term low temperatures, even at the seedling stage. The molecular basis of this phenomenon has not been determined. In a chromatin-level study, we compared the cold-stress reaction of seedlings of two maize inbred lines showing contrasting levels of cold sensitivity. The cold-tolerant line was selected based on field data and previous physiological and transcriptomic level studies. The first condition of gene expression—chromatin accessibility—was assessed by formaldehyde-aided isolation of regulatory elements method and DNA sequencing. Potentially expressed genes and cis-regulatory sequences open for interaction with transcription factors have been defined. The results of this study suggest that during cold stress, the tolerant maize line shifted resources from growth to defense. This shift was shown by potential hormone-level events—degradation of growth-promoting gibberellins and synthesis of jasmonic and abscisic acids. This finding is congruent with the xeromorphic morphology of seedlings of the cold-tolerant line and their ability to regrow when stress ceases. It is a common reaction of cold-tolerant maize lines. Moreover, in the cold-tolerant line, several genes from the low-temperature signaling pathways were potentially expressed. Additionally, numerous stress-response AP2/EREBP-binding cis-motifs were accessible in the cold-tolerant line. Differently in the cold-sensitive B73 line, MADS-binding cis-motifs were the most abundant. Development of the photosynthetic apparatus is crucial for the survival of maize seedlings at low temperature. Our results suggest efficient photosynthesis in seedlings of the cold-tolerant line, as was described earlier in physiological-level analyses.

中文翻译：

---

染色质水平差异阐明了玉米品系中冷敏感性对比水平的潜在决定因素

玉米是亚热带的冷敏感品种。但是，该物种的某些品种即使在幼苗阶段也有可能承受长期低温。这种现象的分子基础尚未确定。在染色质水平的研究中，我们比较了两个玉米自交系幼苗的冷应激反应，显示出不同水平的冷敏感性。耐寒品系是根据田间数据和先前的生理和转录组学水平研究选择的。基因表达的第一个条件——染色质可及性——是通过甲醛辅助的调控元件分离方法和 DNA 测序来评估的。已经定义了与转录因子相互作用的潜在表达基因和顺式调控序列。本研究结果表明，在冷应激期间，宽容的玉米生产线将资源从生长转移到防御。这种转变表现为潜在的激素水平事件——促生长赤霉素的降解以及茉莉酸和脱落酸的合成。这一发现与耐寒品系幼苗的异形形态及其在压力停止时重新生长的能力一致。这是耐寒玉米品系的常见反应。此外，在耐寒品系中，可能表达了来自低温信号通路的几个基因。此外，在耐寒品系中可以获得许多应激反应 AP2/EREBP 结合顺式基序。不同的是，在冷敏感 B73 系中，MADS 结合顺式基序最为丰富。光合装置的发育对于玉米幼苗在低温下的存活至关重要。