Key Lab of Plant-Soil Interaction, MOE, College of Resources and Environmental Sciences, China Agricultural University, Beijing, China.
Lancaster Environment Centre, Lancaster University, Lancaster, UK.
J Exp Bot. 2020 Jul 25;71(15):4547-4561. doi: 10.1093/jxb/eraa116.
Plants can develop root systems with distinct anatomical features and morphological plasticity to forage nutrients distributed heterogeneously in soils. Lateral root proliferation is a typical nutrient-foraging response to a local supply of nitrate, which has been investigated across many plant species. However, the underlying mechanism in maize roots remains largely unknown. Here, we report on identification of a maize truncated MIKC-type MADS-box transcription factor (ZmTMM1) lacking K- and C-domains, expressed preferentially in the lateral root branching zone and induced by the localized supply of nitrate. ZmTMM1 belongs to the AGL17-like MADS-box transcription factor family that contains orthologs of ANR1, a key regulator for root nitrate foraging in Arabidopsis. Ectopic overexpression of ZmTMM1 recovers the defective growth of lateral roots in the Arabidopsis anr1 agl21 double mutant. The local activation of glucocorticoid receptor fusion proteins for ZmTMM1 and an artificially truncated form of AtANR1 without the K- and C-domains stimulates the lateral root growth of the Arabidopsis anr1 agl21 mutant, providing evidence that ZmTMM1 encodes a functional MADS-box that modulates lateral root development. However, no phenotype was observed in ZmTMM1-RNAi transgenic maize lines, suggesting a possible genetic redundancy of ZmTMM1 with other AGL17-like genes in maize. A comparative genome analysis further suggests that a nitrate-inducible transcriptional regulation is probably conserved in both truncated and non-truncated forms of ZmTMM1-like MADS-box transcription factors found in grass species.
植物可以形成具有明显解剖特征和形态可塑性的根系，以在土壤中不均匀分布的养分。侧根增殖是一种典型的养分觅食反应，对硝酸盐的局部供应有反应，这在许多植物物种中都有研究。然而，玉米根系的潜在机制在很大程度上仍然未知。在这里，我们报道了一种玉米截断的 MIKC 型 MADS 盒转录因子（ZmTMM1）的鉴定，该因子缺乏 K 和 C 结构域，在侧根分枝区表达，并受硝酸盐局部供应的诱导。ZmTMM1属于 AGL17 样 MADS 盒转录因子家族，该家族含有拟南芥根硝酸盐觅食关键调节因子 ANR1 的同源物。ZmTMM1 的异位过表达恢复了拟南芥 anr1 agl21 双突变体中侧根生长的缺陷。ZmTMM1和人工截断的 AtANR1（无 K 和 C 结构域）的糖皮质激素受体融合蛋白的局部激活刺激了拟南芥 anr1 agl21 突变体的侧根生长，这表明 ZmTMM1 编码一种功能性 MADS 盒，调节侧根发育。然而，在 ZmTMM1-RNAi 转基因玉米品系中没有观察到表型，这表明 ZmTMM1 与玉米中其他 AGL17 样基因可能存在遗传冗余。比较基因组分析进一步表明，在草物种中发现的截断和非截断形式的 ZmTMM1 样 MADS 盒转录因子中，硝酸盐诱导的转录调控可能是保守的。
