Nitrogen deficiency induces leaf senescence. However, whether or how nitrate might affect this process remains to be investigated. Here, we report an interesting finding that nitrate-- instead of nitrogen--starvation ...Nitrogen deficiency induces leaf senescence. However, whether or how nitrate might affect this process remains to be investigated. Here, we report an interesting finding that nitrate-- instead of nitrogen--starvation induced early leaf senescence in nrtf.5 mutant, and present genetic and physiological data demon-strating that nitrate starvation-induced leaf senescence is suppressed by NRTI.5. NRT1.5 suppresses the senescence process dependent on its function from roots, but not the nitrate transport function. Further analyses using nrt1.5 single and nial nia2 nrt1.5-4 triple mutant showed a negative correlation between nitrate concentration and senescence rate in leaves. Moreover, when exposed to nitrate starvation, foliar potassium level decreased in nrt1.5, but adding potassium could essentially restore the early leaf senescence phenotype of nrt1.5 plants. Nitrate starvation also downregulated the expression of HAK5, RAP2.11, and ANN1 in nrt1.5 roots, and appeared to alter potassium level in xylem sap from nrt1.5. These data suggest that NRT1.5 likely perceives nitrate starvation-derived signals to prevent leaf senescence by facilitating foliar potassium accumulation.展开更多
【目的】研究了进一步解析乙烯对油菜生长后期硝态氮(NO_3~–)再利用的影响,揭示植株生长后期氮素再利用的生理机制。【方法】以氮高效油菜品种湘油15(27号)与氮低效油菜品种814(6号)为试验材料,在15mmol/L氮水平下,每7天浇灌一次50 m L...【目的】研究了进一步解析乙烯对油菜生长后期硝态氮(NO_3~–)再利用的影响,揭示植株生长后期氮素再利用的生理机制。【方法】以氮高效油菜品种湘油15(27号)与氮低效油菜品种814(6号)为试验材料,在15mmol/L氮水平下,每7天浇灌一次50 m L 100μmol/L 1-氨基环丙烷-1-羧酸(1-am-inocyclopropane-1-carboxylic acid,简称ACC),研究ACC对植物生长后期(花期、收获期)氮素再利用的影响及其与氮素利用效率(NUE)的关系。并用拟南芥野生型(col.0)和突变体(nrt1.5)材料作为验证,分别于玻璃顶网室和22℃恒温培养室进行砂培试验。【结果】ACC处理显著抑制了油菜Bn NRT1.5的表达,且植株的衰老可以显著诱导Bn NRT1.5的表达。相对于对照处理,ACC处理植株韧皮部汁液NO_3~–的再转运能力显著降低,导致下部叶NO_3~–含量显著升高,中部叶NO_3~–含量显著下降,上部叶NO_3~–含量无显著变化,进而导致植株含氮量和籽粒含氮量显著提高,以及以生物量和籽粒产量为基础的氮素利用效率(NUE)显著降低。由此推测,油菜生长后期氮素的再利用能力受到NRT1.5基因的显著调控。拟南芥野生型和突变体材料的验证结果表明,相对于拟南芥野生型(col.0)材料,拟南芥nrt1.5植株生长后期相对于col.0有更多的NO_3~–累积在植株衰老叶片中,更少的NO_3~–通过韧皮部转运到生长旺盛的新叶,植物生长后期氮素从老叶向新叶转运的再利用能力显著降低。【结论】油菜生长后期氮素的再利用能力受到ACC的显著调控,油菜和拟南芥NRT1.5基因表达量分别受到抑制或者发生基因突变时,会导致植株韧皮部汁液NO_3~–再转运量减少,更多NO_3~–累积在衰老叶片中而不能得以高效的再利用。因此,调控油菜生长后期NRT1.5的表达,提高油菜生长后期氮素的再转运和利用可以作为提高氮素利用效率的有效手段。展开更多
基金This work was supported by the National Science Foundation of China （Grants 31325003, 31421093）, the Ministry of Agriculture of China （Grant 2014ZX08009-003-005）, and partially by the SA-SIBS Scholarship program.ACKNOWLEDGMENTS We thank Dr. Yi-Fang Tsay （Institute of Molecular Biology, Academia Sinica） for kindly providing the seeds of nrtl.5-1 and ch11-5 Dr. YongFei Wang （Shanghai Institutes for Biological Sciences） for kindly providing the seeds of slah2 and slah3-4 and Dr. Remy Gibrat （Universite Montpellier 2） for kindly providing the seeds of naxt-RNAi. No conflict of interest declared,
文摘Nitrogen deficiency induces leaf senescence. However, whether or how nitrate might affect this process remains to be investigated. Here, we report an interesting finding that nitrate-- instead of nitrogen--starvation induced early leaf senescence in nrtf.5 mutant, and present genetic and physiological data demon-strating that nitrate starvation-induced leaf senescence is suppressed by NRTI.5. NRT1.5 suppresses the senescence process dependent on its function from roots, but not the nitrate transport function. Further analyses using nrt1.5 single and nial nia2 nrt1.5-4 triple mutant showed a negative correlation between nitrate concentration and senescence rate in leaves. Moreover, when exposed to nitrate starvation, foliar potassium level decreased in nrt1.5, but adding potassium could essentially restore the early leaf senescence phenotype of nrt1.5 plants. Nitrate starvation also downregulated the expression of HAK5, RAP2.11, and ANN1 in nrt1.5 roots, and appeared to alter potassium level in xylem sap from nrt1.5. These data suggest that NRT1.5 likely perceives nitrate starvation-derived signals to prevent leaf senescence by facilitating foliar potassium accumulation.
文摘【目的】研究了进一步解析乙烯对油菜生长后期硝态氮(NO_3~–)再利用的影响,揭示植株生长后期氮素再利用的生理机制。【方法】以氮高效油菜品种湘油15(27号)与氮低效油菜品种814(6号)为试验材料,在15mmol/L氮水平下,每7天浇灌一次50 m L 100μmol/L 1-氨基环丙烷-1-羧酸(1-am-inocyclopropane-1-carboxylic acid,简称ACC),研究ACC对植物生长后期(花期、收获期)氮素再利用的影响及其与氮素利用效率(NUE)的关系。并用拟南芥野生型(col.0)和突变体(nrt1.5)材料作为验证,分别于玻璃顶网室和22℃恒温培养室进行砂培试验。【结果】ACC处理显著抑制了油菜Bn NRT1.5的表达,且植株的衰老可以显著诱导Bn NRT1.5的表达。相对于对照处理,ACC处理植株韧皮部汁液NO_3~–的再转运能力显著降低,导致下部叶NO_3~–含量显著升高,中部叶NO_3~–含量显著下降,上部叶NO_3~–含量无显著变化,进而导致植株含氮量和籽粒含氮量显著提高,以及以生物量和籽粒产量为基础的氮素利用效率(NUE)显著降低。由此推测,油菜生长后期氮素的再利用能力受到NRT1.5基因的显著调控。拟南芥野生型和突变体材料的验证结果表明,相对于拟南芥野生型(col.0)材料,拟南芥nrt1.5植株生长后期相对于col.0有更多的NO_3~–累积在植株衰老叶片中,更少的NO_3~–通过韧皮部转运到生长旺盛的新叶,植物生长后期氮素从老叶向新叶转运的再利用能力显著降低。【结论】油菜生长后期氮素的再利用能力受到ACC的显著调控,油菜和拟南芥NRT1.5基因表达量分别受到抑制或者发生基因突变时,会导致植株韧皮部汁液NO_3~–再转运量减少,更多NO_3~–累积在衰老叶片中而不能得以高效的再利用。因此,调控油菜生长后期NRT1.5的表达,提高油菜生长后期氮素的再转运和利用可以作为提高氮素利用效率的有效手段。
