Data_Sheet_4_Iron Deficiency Leads to Chlorosis Through Impacting Chlorophyll Synthesis and Nitrogen Metabolism in Areca catechu L..XLSX

Deficiency of certain elements can cause leaf chlorosis in Areca catechu L. trees, which causes considerable production loss. The linkage between nutrient deficiency and chlorosis phenomenon and physiological defect in A. catechu remains unclear. Here, we found that low iron supply is a determinant for chlorosis of A. catechu seedling, and excessive iron supply resulted in dark green leaves. We also observed morphological characters of A. catechu seedlings under different iron levels and compared their fresh weight, chlorophyll contents, chloroplast structures and photosynthetic activities. Results showed that iron deficiency directly caused chloroplast degeneration and reduced chlorophyll synthesis in chlorosis leaves, while excessive iron treatment can increase chlorophyll contents, chloroplasts sizes, and inflated starch granules. However, both excessive and deficient of iron decreases fresh weight and photosynthetic rate in A. catechu seedlings. Therefore, we applied transcriptomic and metabolomic approaches to understand the effect of different iron supply to A. catechu seedlings. The genes involved in nitrogen assimilation pathway, such as NR (nitrate reductase) and GOGAT (glutamate synthase), were significantly down-regulated under both iron deficiency and excessive iron. Moreover, the accumulation of organic acids and flavonoids indicated a potential way for A. catechu to endure iron deficiency. On the other hand, the up-regulation of POD-related genes was assumed to be a defense strategy against the excessive iron toxicity. Our data demonstrated that A. catechu is an iron-sensitive species, therefore the precise control of iron level is believed to be the key point for A. catechu cultivation.

多种矿质元素缺乏均可导致槟榔（Areca catechu L.）植株出现叶片失绿症，进而造成可观的产量损失。目前，槟榔矿质营养缺乏与叶片失绿现象及生理缺陷之间的关联仍不明确。本研究发现，低铁供应是诱发槟榔幼苗失绿症的关键因素，而高铁供应则会使叶片呈现深绿色。此外，我们观测了不同铁浓度培养下槟榔幼苗的形态特征，并比较了其鲜重、叶绿素含量、叶绿体结构及光合活性。结果显示，缺铁会直接导致失绿叶片的叶绿体退化并抑制叶绿素合成；而高铁处理则可提升叶绿素含量、增大叶绿体体积，并使淀粉粒出现膨大现象。不过，无论是缺铁还是高铁处理，均会降低槟榔幼苗的鲜重与光合速率。为此，我们运用转录组学与代谢组学方法，探究不同铁供应水平对槟榔幼苗的影响。参与氮同化通路的相关基因，如硝酸还原酶（nitrate reductase, NR）与谷氨酸合酶（glutamate synthase, GOGAT），在缺铁及高铁处理下均显著下调表达。此外，有机酸与类黄酮的积累提示槟榔可能存在潜在的缺铁耐受机制。而过氧化物酶（peroxidase, POD）相关基因的上调表达，则被认为是槟榔对抗高铁毒性的防御策略。本研究数据表明，槟榔属于铁敏感物种，因此精准调控铁素水平被认为是槟榔栽培的核心要点。