不同氮效率油菜SPS和PEPC活性差异及其对籽粒产量与油分含量的影响

【目的】蔗糖磷酸合成酶(sucrose phosphate synthase,SPS)与磷酸烯醇式丙酮酸羧化酶(phosphoenolpyruvate carboxylase,PEPC)分别控制着植物体内的碳骨架向碳代谢和氮代谢的流转,影响作物的产量与品质。为探明氮高效油菜品种在高效利用氮素的同时协调籽粒蛋白与油分累积矛盾的机理,研究了不同氮效率油菜品种的SPS与PEPC活性差异及其对籽粒油分含量的影响。【方法】采用土培试验,以氮高效品种27号(H)与氮低效品种6号(L)为试验材料,在常氮(N)与低氮(S)条件下,研究不同氮效率油菜品种苗期到花期叶片与角果发育初期的角果、角果发育中期的角果皮与籽粒中SPS与PEPC活性变化及差异、生长后期碳素转运量与转运率以及收获期籽粒油分含量的差异。【结果】两种供氮水平下,氮高效品种27号的产量与籽粒油分含量均显著高于氮低效品种6号,品种优势明显;且氮高效品种27号苗期到花期叶片与角果发育初期的角果、角果发育中期的角果皮与籽粒中的SPS与PEPC活性均高于氮低效品种6号,两种供氮水平的规律相同,但是SPS与PEPC活性的比值(SPS/PEPC)却因生育期不同而异,营养生长期叶片中氮高效品种27号的SPS/PEPC高于氮低效品种6号,开花期品种间叶片SPS/PEPC相近,角果发育期主要生殖器官中的SPS/PEPC值氮高效品种反而低于氮低效品种。说明氮高效品种向碳代谢和氮代谢输送的碳骨架在全生育期均多于氮低效品种,而碳代谢对氮代谢的响应只在生育前期强于氮低效品种,生育后期则相反。碳素转运量与转运率、籽粒油分含量与产量也是氮高效品种大于氮低效品种,这可能为氮高效品种协调籽粒蛋白与油分累积矛盾的重要生理机制。供氮水平对上述各指标有不同的影响,籽粒产量、PEPC活性、碳素转运量及转运率以常氮处理高于低氮处理,而油分含量、SPS活性及SPS/PEPC以常氮处理低于低氮处理,但不改变以上指标的品种间差异。【结论】与氮低效品种相比,氮高效品种全生育期向碳、氮代谢均输送更多的碳骨架,这是氮高效品种缓解碳、氮代谢矛盾的重要前提;碳代谢对氮代谢的响应生育前期较高、生育后期较低,同时生育后期有更多营养器官的碳素转运到籽粒,也为油菜生育后期满足籽粒碳、氮代谢所需要的碳骨架,并协调籽粒油分与蛋白质含量的矛盾提供了条件。

Different activities of SPS and PEPC in oilseed rape with different nitrogen use efficiency and their influence on seed yield and oil-content

【Objectives】 Transportation of carbon skeleton into carbon metabolism pathway and nitrogen metabolism circulation were respectively controlled by SPS (sucrose phosphate synthase) and PEPC (phosphoenolpyruvate carboxylase), and then the yield and grain quality of crop were affected by the two enzymes. In order to elucidate the regulation mechanism of contradiction between seed protein and oil during the high nitrogen use efficiency (NUE) progress in oilseed rape with high N efficiency, the different activities of SPS and PEPC and their influence on seed yield and oil content in oilseed rape with different NUE were studied in this paper.【Methods】 Variety No.27 with high NUE (H) and variety No.6 with low NUE (L) were cultured in soil under different nitrogen conditions [normal nitrogen condition(N) and nitrogen stress condition(S)] to study the difference of enzyme activities (SPS and PEPC) in leaf from seedling stage to flowering stage, in silique at early silique stage and in grain and silique husk at silique mid-term stage between the two NUE rape varieties as well as carbon (C) transportation amount and rate and their seed yield and seed oil content. 【Results】The test results showed that seed yield and seed oil content of high NUE (No.27) variety were significantly higher than those of low NUE (No.6) variety under two nitrogen conditions(normal nitrogen and nitrogen stress), the high NUE rape showed obvious variety advantage. Moreover, activities of SPS and PEPC of high NUE (No.27) variety in leaf from seedling stage to flowering stage were higher than those of low NUE (No.6) variety under two nitrogen conditions, the same tendency was found in silique at early silique stage as well as in grain and silique husk at silique mid-term stage. While the SPS/PEPC of the two variety rape was changed at different growth periods, SPS/PEPC of high NUE (No.27) variety in leaf at vegetative stage was higher than those of low NUE (No.6) variety, SPS/PEPC of the two varieties rape was similar in leaf at flowering stage, instead SPS/PEPC in main reproduction organs at silique stage of high NUE (No.27) variety was lower compared to low NUE (No.6) variety, which revealed that amount of delivery of carbon skeleton to C metabolism and N assimilation of high NUE (No.27) variety was more than those of low NUE (No.6) variety during the whole growth period and the response of C metabolism to N assimilation of high NUE (No.27) variety was higher than those of low NUE (No.6) variety at early growth stage, while at late growth stage the response of response of high NUE (No.27) variety was lower than that of low NUE (No.6) variety. Meanwhile C transportation amount and rate of high NUE (No.27) variety were significantly higher than those of low NUE (No.6) variety, which might be the vital physiological mechanism that regulatingthe contradiction between seed protein and oil during the high nitrogen use efficiency (NUE) progress in oilseed rape with high N efficiency. As for influence of different nitrogen conditions on items which we tested above, the results showed that seed yield, activity of PEPC, carbon transportation amount and rate were higher under normal nitrogen condition than under nitrogen stress condition, but seed oil content, activity of SPS, SPS/PEPC showed an inverse law, these phenomena appeared in the two rape varieties.【Conclusions】Compared to low NUE (No.6) variety, more carbon skeleton was transported into C and N metabolism pathway in high NUE (No.27) variety during the whole growth stage. This was the important premise for HNUE variety to coordinate the contradiction between C and N metabolisms. Response of C metabolism to N assimilation was higher during earlier growth stage than during later growth stage. Meanwhile, higher proportion of C in vegetative organs was transported into seed during later growth stage, which met the demands of carbon skeleton in C and N metabolism and coordinated the contradiction between seed oil and protein contents during later growth stage.