Strigolactones Decrease Leaf Angle in Response to Nutrient Deficiencies in Rice
Strigolactones Decrease Leaf Angle in Response to Nutrient Deficiencies in Rice
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DOI：
10.3389/fpls.2020.00135
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发表时间：
2020-02
影响因子：
5.6
通讯作者：
M. Shindo;Shuku Yamamoto;K. Shimomura;Mikihisa Umehara
中科院分区：
文献类型：
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作者：
M. Shindo;Shuku Yamamoto;K. Shimomura;Mikihisa Umehara
独脚金内酯（Strigolactones，SL）是一类由β-胡萝卜素经DWARF（D）27、D17、D10和OsMORE AXILLARY GROWTH（MAX）1催化的连续反应合成的植物激素。在水稻中，内源SL水平增加响应于氮、磷酸盐或硫酸盐（−N、−P或−S）的缺乏。水稻SL突变体表现出增加叶片关节（LJ）的角度，以及矮化，延迟叶片衰老，并增强芽分枝。LJ角是决定植物构型的重要性状。为了评估内源SL对水稻LJ角的影响，我们在大量营养素缺乏的情况下测量了LJ角并分析了SL生物合成基因的表达。在“盐狩”背景下，SL突变体的LJ角显著大于野生型（WT）。在WT和SL-生物合成突变体中，用SL合成类似物GR 24直接处理降低了LJ角。在WT中，缺乏N、P或S，但不缺乏K、Ca、Mg或Fe，会降低LJ角。在SL突变体中，N、P或S的缺乏没有这种影响。我们分析了SL相关基因在N、P或S缺乏的WT LJ中表达的时间过程，发现SL生物合成基因的表达在缺乏发作后2或3天增加。SL-生物合成和信号基因的表达水平在−P下特别强烈地增加。水稻品种“日本晴”、“Norin 8”和“Kasalath”的LJ角比“盐狩”大，有趣的是WT和SL突变体之间没有显著差异。在“日本晴”中，内源SL水平增加，LJ角减小下-N和-P。这些结果表明，SL水平增加响应营养不足，和内源SL的升高可能负调节水稻叶角。
Strigolactones (SLs) are a class of plant hormones that are synthesized from β-carotene through sequential reactions catalyzed by DWARF (D) 27, D17, D10, and OsMORE AXILLARY GROWTH (MAX) 1 in rice (Oryza sativa L.). In rice, endogenous SL levels increase in response to deficiency of nitrogen, phosphate, or sulfate (−N, −P, or −S). Rice SL mutants show increased lamina joint (LJ) angle as well as dwarfism, delayed leaf senescence, and enhanced shoot branching. The LJ angle is an important trait that determines plant architecture. To evaluate the effect of endogenous SLs on LJ angle in rice, we measured LJ angle and analyzed the expression of SL-biosynthesis genes under macronutrient deficiencies. In the “Shiokari” background, LJ angle was significantly larger in SL mutants than in the wild-type (WT). In WT and SL-biosynthesis mutants, direct treatment with the SL synthetic analog GR24 decreased the LJ angle. In WT, deficiency of N, P, or S, but not of K, Ca, Mg, or Fe decreased LJ angle. In SL mutants, deficiency of N, P, or S had no such effect. We analyzed the time course of SL-related gene expression in the LJ of WT deficient in N, P, or S, and found that expression of SL-biosynthesis genes increased 2 or 3 days after the onset of deficiency. Expression levels of both the SL-biosynthesis and signaling genes was particularly strongly increased under −P. Rice cultivars “Nipponbare”, “Norin 8”, and “Kasalath” had larger LJ angle than “Shiokari”, interestingly with no significant differences between WT and SL mutants. In “Nipponbare”, endogenous SL levels increased and the LJ angle was decreased under −N and −P. These results indicate that SL levels increased in response to nutrient deficiencies, and that elevated endogenous SLs might negatively regulate leaf angle in rice.