Aims

BnaC4.BOR1;1c is required for B acquisition in Brassica napus (B. napus) under low B stress. This study aimed to reveal the B regulatory mechanism of BnaC4.BOR1;1c and its physiological roles in B translocation from roots to shoots and B distribution in shoots.

Methods

Transgenic Arabidopsis plants expressing GUS (β-glucuronidase) under different promoters were generated and the mRNA, and GUS activity was quantitatively measured. The in-situ PCR and immunohistochemistry in B. napus were performed to investigate BnaC4.BOR1;1c expression pattern and localization. Furthermore, assays of B transport and distribution in wild type B. napus and BnaC4.BOR1;1c RNAi lines were carried out to elucidate its physiological roles.

Results

Results showed that BnaC4.BOR1;1c mRNA abundance is negatively correlated with B availability, which was mediated by the 29 nt sequence in the 5′ terminal region of 5’-UTR. Besides, the 5’-UTR simultaneously regulates protein expression level, most probably depending on the translation efficiency. BnaC4.BOR1;1c mainly localizes on the plasma membrane of vascular bundle cells in roots and shoots with a polar localization manner that is probably beneficial to B xylem loading in roots and B unloading from xylem to phloem in vascular bundle of shoots. Short-term ¹⁰B uptake analysis demonstrates that BnaC4.BOR1;1c preferentially distributes B to developing leaves and flowers under B deficiency.

Conclusion

This study reveals combined regulatory action of mRNA abundance and translation efficiency mediated by the 5’-UTR in BnaC4.BOR1;1c in response to B availability and its physiological role in preferential B acquisition in developing tissues of B. napus.

中文翻译：

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BnaC4.BOR1; 1c（一种外排硼转运蛋白基因）的血管组织特异性表达受硼可用性的调节，可有效促进甘蓝型油菜的硼吸收

目的

在低B胁迫下，甘蓝型油菜（B. napus）中的B采集需要BnaC4.BOR1; 1c。这项研究旨在揭示BnaC4.BOR1; 1c的B调控机制及其在B从根到芽的转运以及B在芽中的分布的生理作用。

方法

产生了在不同启动子下表达GUS（β-葡萄糖醛酸苷酶）的转基因拟南芥植物，并检测了其mRNA和GUS活性。进行了油菜双歧杆菌的原位PCR和免疫组化研究，以研究BnaC4.BOR1; 1c的表达模式和定位。此外，测定了B在野生型油菜和BnaC4.BOR1; 1c RNAi系中的运输和分布，以阐明其生理作用。

结果

结果表明，BnaC4.BOR1; 1c mRNA的丰度与B的利用率呈负相关，这是由5'-UTR的5'末端区域中的29 nt序列介导的。此外，5'-UTR同时调节蛋白质表达水平，很可能取决于翻译效率。BnaC4.BOR1; 1c主要以极性定位方式定位在根和芽中的维管束细胞的质膜上，这可能有利于根中B木质部的负载和维管束中B从木质部到韧皮部的卸载。短期¹⁰ B吸收分析表明，在B缺乏的情况下，BnaC4.BOR1; 1c会将B优先分配给正在发育的叶片和花朵。

结论

这项研究揭示了BnaC4.BOR1; 1c中5'-UTR介导的对mRNA丰度和翻译效率的联合调节作用，响应于B的有效性及其在发育中的B. napus组织中优先获得B的生理作用。