華中農(nóng)業(yè)大學(xué)學(xué)者在甘藍(lán)型油菜硼吸收轉(zhuǎn)運(yùn)的分子機(jī)制研究中取得新進(jìn)展

　　植物營(yíng)養(yǎng)生物團(tuán)隊(duì)從甘藍(lán)型油菜中鑒定到兩個(gè)硼轉(zhuǎn)運(yùn)基因BnaC4.BOR2和BnaA4.BOR2，進(jìn)一步基于CRISPR/Cas9基因編輯系統(tǒng)成功建立了BnaC4.BOR2和BnaA4.BOR2的油菜突變體?；谶@些遺傳材料，在營(yíng)養(yǎng)液培養(yǎng)體系和盆栽體系中深入開展了系統(tǒng)的生物化學(xué)以及分子生物學(xué)研究。結(jié)果表明，BnaC4.BOR2主要在根尖側(cè)根冠、中柱、葉片和花器官中表達(dá)，在根尖硼獲取、中柱硼運(yùn)輸以及花器官硼供應(yīng)中起著重要的作用。BnaA4.BOR2基因主要在根系維管組織和花器官中表達(dá)，負(fù)責(zé)將根系中的硼向地上部轉(zhuǎn)運(yùn)，維持花器官硼供應(yīng)。此外，研究還發(fā)現(xiàn)BnaC4.BOR2與硼酸通道基因BnaA2.NIP5;1和BnaA3.NIP5;1在根中存在很強(qiáng)的協(xié)調(diào)作用，但相關(guān)機(jī)制仍有待剖析。綜上所述，該研究成功從甘藍(lán)型油菜中鑒定兩個(gè)硼轉(zhuǎn)運(yùn)基因并深入系統(tǒng)的揭示了硼從根到花的精確轉(zhuǎn)運(yùn)過程，為進(jìn)一步理解油菜硼的吸收運(yùn)輸機(jī)理提供了理論基礎(chǔ)和硼高效育種提供了基因資源。

 

　　我校博士研究生劉威為論文第一作者，汪社亮副教授和徐芳森教授分別為Plant, Cell and Environment和Plant Physiology and Biochemistry論文通訊作者。我校的葉祥盛研究員、蔡紅梅副教授、石磊教授也參與了該項(xiàng)研究。該研究得到了國(guó)家自然科學(xué)基金和國(guó)家重點(diǎn)研發(fā)計(jì)劃項(xiàng)目的資助。

 

　　【英文摘要1】

 

　　Boron （B） is an essential microelement in plant growth and development. However, the molecular mechanisms underlying B uptake and translocation in Brassica napus are poorly understood. Herein, we identified a low-B-inducible gene, namely BnaC4.BOR2, with high transcriptional activity in root tips, stele cells, leaves, and floral organs. The GFP labeled BnaC4.BOR2 protein was localized to the plasma membrane to demonstrate the B efflux activity in yeast and Arabidopsis. BnaC4.BOR2 knockout considerably reduced B concentration in the root and xylem sap, and altered B distribution in different organs at low B supply, exacerbating B sensitivity at the vegetative and reproductive stages. Additionally, the grafting experiment showed that BnaC4.BOR2 expression in the roots contributed more to B deficiency adaptability than that in the shoots. The pot experiments with low-B-soil revealed B concentration in leaves and siliques of BnaC4.BOR2 mutants were markedly reduced, showing an obvious B-deficient phenotype of “flowering without seed setting” and a considerable reduction in seed yield in B-deficient soil. Altogether, the findings of this study highlight the crucial role of BnaC4.BOR2 in B uptake and translocation during B. napus growth and seed yield under low-B conditions.

 

　　【英文摘要2】

 

　　Boron （B） is essential for plant growth. However, the molecular mechanism of B transport in rapeseed （Brassica napus L.） is unknown well. Here, we report that B transporter BnaA4.BOR2 is involved in the transport of B from root to shoot and its distribution in shoot cell wall and flower in rapeseed. The results of GUS staining and in-situ PCR analysis showed that BnaA4.BOR2 is mainly expressed in cortex and endodermis of root tip meristem zone and endodermis of mature zone. BnaA4.BOR2 was mainly localized in plasma membrane and showed B transport activity in yeast. Overexpression of Bna4.BOR2 could rescue the phenotype of Arabidopsis mutant bor2-2 under low-B condition. Furthermore, knockout of BnaA4.BOR2 could significantly enhance the sensitivity of rapeseed mutants to B deficiency, including inhibition of root elongation and biomass decrease of roots and shoots. The B concentration in xylem sap of BnaA4.BOR2 mutants was significantly decreased under B deficiency, which resulted in significantly lower B concentrations in shoot cell wall at seedling stage and flower organ at reproductive stage compared to that of wild-type QY10. The growth of BnaA4.BOR2 mutants were severely inhibited, exhibiting a typical B-deficient phenotype of “flowering without seed setting”， leading to a sharp decrease in seed yield in B deficient soil. Taken together, these results indicate that BnaA4.BOR2 is critical for rapeseed growth and seed yield production under low B level, which is mainly expressed in cortex and endodermis, and contributed to the transport of B from roots to shoots and its distribution in shoot.