近日，華中農業大學資源與環境學院植物營養生物學團隊研究成果“The transcription factor BnaA9.WRKY47 coordinates leaf senescence and nitrogen remobilization in Brassica napus”在植物學雜志Journal of Experimental Botany上發表。
甘藍型油菜根系吸收的總氮中，大約48%從營養組織回收到成熟的種子中，另外大約15%的氮因落葉而損失。因此，改善衰老葉片中的氮素回收，提高氮素再利用效率十分重要。研究發現，BnaA9.WRKY47超表達植株表現出葉片提前衰老，葉綠體降解的表型。BnaA9.WRKY47超表達株系的籽粒產量較野生型顯著提高；相反，BnaA9.WRKY47功能缺失突變體的產量降低。
通過生化實驗分析，研究團隊發現BnaA9.WRKY47直接激活持綠基因BnaC7.SGR1以加速老葉黃化衰老。研究表明伴隨著缺氮誘導的葉片衰老，超表達株系老葉中氨基酸濃度升高，氮素再分配能力提高。同時BnaA9.WRKY47能夠協同激活氨基酸滲透酶BnaA9.AAP1和硝酸鹽轉運蛋白BnaA2.NTR1.7。因此，研究團隊提出缺氮脅迫下油菜提高氮素再利用理論模型：缺氮上調老葉BnaA9.WRKY47基因的表達，增加老葉中BnaA9.WRKY47蛋白豐度，BnaA9.WRKY47上調了BnaC7.SGR1、BnaA2.NRT1.7和BnaA9.AAP1的表達，從而促進了甘藍型油菜老葉的衰老以及氮素向新生組織或種子的再轉運，有利于缺氮脅迫下油菜達到養分資源配置最大化。
華中農業大學植物營養生物學團隊博士研究生崔蕊為論文第一作者，徐芳森教授和汪社亮副教授為共同通訊作者，我校石磊教授、已畢業博士馮英娜和碩士研究生姚金亮也參與了該項研究。該研究得到了國家重點研發計劃和國家自然科學基金的支持。
論文鏈接：/file/upload/2023-08-10/nrro52gh4ky
英文摘要：
Nitrogen （N） is an essential macronutrient for plants, and N remobilization is key for plant adaptation to N deficiency stress. However, there is a limited understanding of the regulatory mechanisms of N remobilization in Brassica napus. Here, we report a transcription factor, BnaA9.WRKY47, induced by N starvation. At the seedling stage, BnaA9.WRKY47-OE lines displayed earlier senescence of older leaves and preferential growth of juvenile leaves compared to the wild-type 'Westar 10' under N starvation. At the field scale, the seed yield was significantly increased in BnaA9.WRKY47-OE lines compared to 'Westar 10' grown under N deficiency conditions and, conversely, reduced in BnaA9.WRKY47-mutants. Biochemical analyses demonstrate that BnaA9.WRKY47 directly activates BnaC7.SGR1 to accelerate older leaf senescence. In line with leaf senescence, the amino acid concentration was elevated, and the N distribution was reduced in the older leaves of OE lines. This result is because BnaA9.WRKY47 activates the amino acid permease BnaA9.AAP1 and the nitrate transporter BnaA2.NRT1.7. Therefore, the expression of BnaA9.WRKY47 efficiently facilitates N remobilization from older to younger leaves or seeds. Taken together, the results of this study demonstrate that BnaA9.WRKY47 upregulates the expression of BnaC7.SGR1, BnaA2.NRT1.7 and BnaA9AAP1 thus promoting the remobilization of N in B. napus under N starvation.
