华中农业大学学者在甘蓝型油菜硼吸收转运的分子机制研究中取得新进展

　　植物营养生物团队从甘蓝型油菜中鉴定到两个硼转运基因BnaC4.BOR2和BnaA4.BOR2，进一步基于CRISPR/Cas9基因编辑系统成功建立了BnaC4.BOR2和BnaA4.BOR2的油菜突变体。基于这些遗传材料，在营养液培养体系和盆栽体系中深入开展了系统的生物化学以及分子生物学研究。结果表明，BnaC4.BOR2主要在根尖侧根冠、中柱、叶片和花器官中表达，在根尖硼获取、中柱硼运输以及花器官硼供应中起着重要的作用。BnaA4.BOR2基因主要在根系维管组织和花器官中表达，负责将根系中的硼向地上部转运，维持花器官硼供应。此外，研究还发现BnaC4.BOR2与硼酸通道基因BnaA2.NIP5;1和BnaA3.NIP5;1在根中存在很强的协调作用，但相关机制仍有待剖析。综上所述，该研究成功从甘蓝型油菜中鉴定两个硼转运基因并深入系统的揭示了硼从根到花的精确转运过程，为进一步理解油菜硼的吸收运输机理提供了理论基础和硼高效育种提供了基因资源。

 

　　我校博士研究生刘威为论文第一作者，汪社亮副教授和徐芳森教授分别为Plant, Cell and Environment和Plant Physiology and Biochemistry论文通讯作者。我校的叶祥盛研究员、蔡红梅副教授、石磊教授也参与了该项研究。该研究得到了国家自然科学基金和国家重点研发计划项目的资助。

 

　　【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.