Regulation of root hair density by phosphorus availability in Arabidopsis thaliana
Regulation of root hair density by phosphorus availability in Arabidopsis thaliana
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DOI：
10.1046/j.1365-3040.2001.00695.x
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发表时间：
2001-04-01
影响因子：
7.3
通讯作者：
Lynch, JP
中科院分区：
文献类型：
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作者：
Ma, Z;Bielenberg, DG;Lynch, JP
研究了拟南芥根毛密度对磷有效性的响应。拟南芥在不同磷浓度的培养基中无菌生长，磷浓度从1 mmol m（-3）到2000 mmol m（-3）不等。从生长第7天开始分析根毛密度（每毫米根长根毛数）。根毛密度受磷速效度的高度调控，在低磷速效条件下，根毛密度显著增加。根毛生长初期对磷速效不敏感，生长第9 d后开始响应。低磷（1 mmol m-3）培养基的根毛密度约为高磷（1000 mmol m-3）培养基的5倍。在此范围内，根毛密度随磷浓度的增加呈对数递减。根毛密度在其他几种营养物质缺乏的情况下也会增加，但不如低磷的情况强烈。吲哚乙酸（IAA）、生长素转运抑制剂2-（对氯苯氧基）-2-甲基丙酸（CMPA）、乙烯前体1-氨基环丙烷-1-羧酸（ACC）和乙烯合成抑制剂氨基乙酸（AOA）在高磷条件下均能增加根毛密度，但在低磷条件下作用很小。低磷显著改变了根的解剖结构，导致根直径增加9%，单个毛胚细胞的横截面积减少31%，单个成膜细胞的横截面积减少40%，横截面积增加45%的皮质细胞。低磷根皮层细胞数量较多，表皮细胞尺寸较小，毛原细胞锉数由8个增加到12个。低磷根中根毛密度增加的三分之二是由于毛原细胞形成毛发的可能性增加引起的，而33%的增加是由于低磷根解剖结构的变化导致毛原细胞锉数增加。这些结果表明，磷的有效性可以从根本上改变根的解剖结构，导致根毛密度的变化，这可能对磷的获取很重要。
We characterized the response of root hair density to phosphorus (P) availability in Arabidopsis thaliana. Arabidopsis plants were grown aseptically in growth media with varied phosphorus concentrations, ranging from 1 mmol m(-3) to 2000 mmol m(-3) phosphorus. Root hair density (number of root hairs per mm of root length) was analysed starting at 7 d of growth. Root hair density was highly regulated by phosphorus availability, increasing significantly in roots exposed to low-phosphorus availability, The initial root hairs produced by the radicle were not sensitive to phosphorus availability, but began to respond after 9 d of growth. Root hair density was about five times greater in low phosphorus (1 mmol m-3) than in high phosphorus (1000 mmol m(-3)) media. Root hair density decreased logarithmically in response to increasing phosphorus concentrations within that range. Root hair density also increased in response to deficiencies of several other nutrients, but not as strongly as to low phosphorus. Indoleacetic acid (IAA), the auxin transport inhibitor 2-(p-chlorophenoxy)-2-methylpropionic acid (CMPA), the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), and the ethylene synthesis inhibitor aminooxyacetic acid (AOA) all increased root hair density under high phosphorus but had very little effect under low phosphorus. Low phosphorus significantly changed root anatomy, causing a 9% increase in root diameter, a 31% decrease in the cross-sectional area of individual trichoblasts, a 40% decrease in the cross-sectional area of individual atrichoblasts, and 45% more cortical cells in cross-section. The larger number of cortical cells and smaller epidermal cell size in low phosphorus roots increased the number of trichoblast files from eight to 12. Two-thirds of increased root hair density in low phosphorus roots was caused by increased likelihood of trichoblasts to form hairs, and 33% of the increase was accounted for by changes in low phosphorus root anatomy resulting in an increased number of trichoblast files. These results show that phosphorus availability can fundamentally alter root anatomy, leading to changes in root hair density, which are presumably important for phosphorus acquisition.