Temperature is a major factor regulating plant growth. To reproduce at extreme temperatures, plants must develop normal reproductive organs when exposed to temperature changes. However, little is known about the underlying molecular mechanisms. Here, we identified the maize (Zea mays) mutant thermosensitive vanishing tassel1-R (tvt1-R), which lacks tassels at high (restrictive) temperatures due to shoot apical meristem (SAM) arrest, but forms normal tassels at moderate (permissive) temperatures. The critical stage for phenotypic conversion in tvt1-R mutants is V2 to V6 (Vn, where "n" is the number of leaves with collars visible). Positional cloning and allelism and complementation tests revealed that a G-to-A mutation causing a Arg₂₇₇-to-His₂₇₇ substitution in ZmRNRL1, a ribonucleotide reductase (RNR) large subunit (RNRL), confers the tvt1-R mutant phenotype. RNR regulates the rate of deoxyribonucleoside triphosphate (dNTP) production for DNA replication and damage repair. By expression, yeast two-hybrid, RNA sequencing, and flow cytometric analyses, we found that ZmRNRL1-tvt1-R failed to interact with all three RNR small subunits at 34°C due to the Arg₂₇₇-to-His₂₇₇ substitution, which could impede RNR holoenzyme (α₂β₂) formation, thereby decreasing the dNTP supply for DNA replication. Decreased dNTP supply may be especially severe for the SAM that requires a continuous, sufficient dNTP supply for rapid division, as demonstrated by the SAM arrest and tassel absence in tvt1-R mutants at restrictive temperatures. Our study reveals a novel mechanism of temperature-gated tassel formation in maize and provides insight into the role of RNRL in SAM maintenance.

温度是调节植物生长的主要因素。为了在极端温度下繁殖，植物在暴露于温度变化时必须发育正常的生殖器官。然而，人们对潜在的分子机制知之甚少。在这里，我们鉴定了玉米（Zea mays）突变体热敏消失流苏1 - R（tvt1 - R），由于茎尖分生组织（SAM）停滞，在高温（限制性）温度下缺乏流苏，但在中等（允许）温度下形成正常流苏温度。tvt1 - R中表型转换的关键阶段突变体是 V2 到 V6（Vn，其中“n”是具有可见项圈的叶子数量）。定位克隆和等位基因和互补测试表明，G-to-A 突变导致ZmRNRL1（一种核糖核苷酸还原酶（RNR）大亚基（RNRL）中的 Arg ₂₇₇ -to- His ₂₇₇取代）赋予tvt1 - R突变表型。RNR 调节脱氧核糖核苷三磷酸 (dNTP) 的生成速率，用于 DNA 复制和损伤修复。通过表达、酵母双杂交、RNA 测序和流式细胞术分析，我们发现 ZmRNRL1- tvt1 - R在 34°C 下未能与所有三个 RNR 小亚基相互作用，因为 Arg ₂₇₇ -to-His ₂₇₇取代，这可能会阻碍 RNR 全酶 (α ₂ β ₂ ) 的形成，从而减少 DNA 复制的 dNTP 供应。对于需要连续、充足的 dNTP 供应以进行快速分裂的 SAM，dNTP 供应减少可能尤其严重，正如在限制温度下tvt1 - R突变体中的 SAM 停滞和流苏缺失所证明的那样。我们的研究揭示了玉米中温度门控雄穗形成的新机制，并提供了对 RNRL 在 SAM 维持中的作用的见解。