Maize (Zea mays) is an important cereal crop with suitable stalk formation which is beneficial for acquiring an ideal agronomic trait to resist lodging and higher planting density. The elongation pattern of stalks arises from the variable growth of individual internodes driven by cell division and cell expansion comprising the maize stalk. However, the spatiotemporal dynamics and regulatory network of the maize stalk development and differentiation process remain unclear. Here, we report spatiotemporally resolved transcriptomes using all internodes of the whole stalks from developing maize at the elongation and maturation stages. We identified four distinct groups corresponding to four developmental zones and nine specific clusters with diverse spatiotemporal expression patterns among individual internodes of the stalk. Through weighted gene coexpression network analysis, we constructed transcriptional regulatory networks at a fine spatiotemporal resolution and uncovered key modules and candidate genes involved in internode maintenance, elongation, and division that determine stalk length and thickness in maize. Further CRISPR/Cas9-mediated knockout validated the function of a cytochrome P450 gene, ZmD1, in the regulation of stalk length and thickness as predicted by the WGCN. Collectively, these results provide insights into the high genetic complexity of stalk development and the potentially valuable resources with ideal stalk lengths and widths for genetic improvements in maize.

中文翻译：

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时空转录组网络动态调节玉米茎的发育

玉米( Zea mays )是一种重要的谷类作物，其秆形成适宜，有利于获得理想的抗倒伏农艺性状和较高的种植密度。茎的伸长模式源于由玉米茎的细胞分裂和细胞扩张驱动的各个节间的可变生长。然而，玉米秆发育和分化过程的时空动力学和调控网络仍不清楚。在这里，我们使用伸长和成熟阶段发育中的玉米的整个茎的所有节间报告了时空解析的转录组。我们确定了四个不同的群体，对应于四个发育区和九个特定的簇，在茎的各个节间之间具有不同的时空表达模式。通过加权基因共表达网络分析，我们以精细的时空分辨率构建了转录调控网络，并发现了参与决定玉米茎长度和厚度的节间维持、伸长和分裂的关键模块和候选基因。进一步的 CRISPR/Cas9 介导的敲除验证了细胞色素 P450 基因ZmD1在调节茎长度和厚度方面的功能，正如 WGCN 预测的那样。总的来说，这些结果为了解茎发育的高遗传复杂性以及具有理想茎长度和宽度的玉米遗传改良的潜在有价值的资源提供了见解。