Table_1_Early Responses of Brassica oleracea Roots to Zinc Supply Under Sufficient and Sub-Optimal Phosphorus Supply.xlsx

Shoot zinc (Zn) concentration in Brassica oleracea is affected by soil Zn and phosphorus (P) supply. Most problematic is the negative impact of P fertilizers on Zn concentrations in crops, which makes balancing yield and mineral quality challenging. To evaluate early molecular mechanisms involved in the accumulation of large shoot Zn concentrations regardless of the P supply, two B. oleracea accessions differing in root architecture and root exudates were grown hydroponically for two weeks with different combinations of P and Zn supply. Ionome profiling and deep RNA sequencing of roots revealed interactions of P and Zn in planta, without apparent phenotypic effects. In addition, increasing P supply did not reduce tissue Zn concentration. Substantial changes in gene expression in response to different P and/or Zn supplies in roots of both accessions ensured nutritionally sufficient P and Zn uptake. Numerous genes were differentially expressed after changing Zn or P supply and most of them were unique to only one accession, highlighting their different strategies in achieving nutrient sufficiency. Thus, different gene networks responded to the changing P and Zn supply in the two accessions. Additionally, enrichment analysis of gene ontology classes revealed that genes involved in lipid metabolism, response to starvation, and anion transport mechanisms were most responsive to differences in P and Zn supply in both accessions. The results agreed with previously studies demonstrating alterations in P and Zn transport and phospholipid metabolism in response to reduced P and Zn supply. It is anticipated that improved knowledge of genes responsive to P or Zn supply will help illuminate the roles in uptake and accumulation of P and Zn and might identify candidate genes for breeding high-yield-high-Zn brassicas.

甘蓝（Brassica oleracea）地上部锌（Zn）浓度受土壤锌与磷（P）供给水平的调控。其中尤以磷肥对作物锌浓度的负面效应最为棘手，这使得平衡作物产量与矿质营养品质的工作颇具挑战。为解析不受磷供给水平影响、实现高地上部锌浓度积累的早期分子机制，本研究选取两个根系构型与根系分泌物存在差异的甘蓝种质系，采用不同磷锌供给组合进行为期两周的水培种植。对根系开展离子组分析（ionome profiling）与深度RNA测序（deep RNA sequencing）后发现，磷与锌在植物体内存在互作，但未产生明显的表型效应。此外，提高磷供给水平并未降低植株组织内的锌浓度。两个种质系的根系基因表达均因不同磷、锌供给组合发生显著变化，以此保障磷与锌的营养摄取充足。改变锌或磷供给水平后，大量基因呈现差异表达，且其中多数仅在单个种质系中特异性表达，这凸显出二者实现营养充足供给的不同策略。由此可见，两个种质系中响应磷锌供给变化的基因调控网络存在差异。此外，基因本体（Gene Ontology, GO）功能富集分析显示，在两个种质系中，参与脂质代谢、饥饿响应以及阴离子转运机制的基因对磷锌供给差异的响应最为显著。本研究结果与此前报道的"磷锌供给不足会引发磷锌转运与磷脂代谢改变"的结论相符。我们预期，深化对响应磷或锌供给的基因的认知，将有助于阐明磷锌摄取与积累的调控机制，并可为培育高产高锌甘蓝品种筛选候选基因。