He Yutong, He Keren, Mai Jingwen, Ou Meiyin, Chen Laibin, Li Yuanyuan, Wan Tao, Gu Luping, Shabala Sergey, Li Xuewen, Li Yalin, Yu Min
International Research Center for Environmental Membrane Biology & Department of Horticulture, Foshan University, Foshan, China.
Department of Biomedical Science, City University of Hong Kong, Hong Kong, China.
Physiol Plant. 2025 Jan-Feb;177(1):e70056. doi: 10.1111/ppl.70056.
Plant architecture and subsequent productivity are determined by the shoot apical dominance, which is disturbed by the deficiency of boron, one of the essential trace elements for plant growth and reproduction. However, the mechanism by which B controls shoot apical dominance or axillary bud outgrows under B deficiency is still unclear. This work aimed to investigate the mechanistic basis of this process, with focus on the interaction between B and polar auxin transport. Adopting an all-buds phenotyping methodology and employing several complementary approaches, we found that boron deficiency inhibited plant growth and changed the shoot architecture, resulting in the outgrowth of axillary buds at nodes 1-3. This was related to the auxin accumulation in shoot apical parts buds under B deficiency. Applying N-1-naphthylphthalamic acid to inhibit auxin transport from the shoot apex promoted the outgrowth of axillary buds in boron-sufficient (+B) plants. In decapitated plants, the application of exogenous auxin to the shoot apex only inhibited the outgrowth of axillary buds in +B plants. At higher auxin doses, the toxic effect of IAA was observed in the lower part of the shoot, which was more severe in +B plants than in B-deprived (-B) plants. Furthermore, the expression of PsPIN3 was significantly downregulated under -B conditions. These results indicate that B deficiency inhibits PAT from the apical bud through the main stem to the lower parts, leading to an increase of auxin level in the apical bud, which inhibits the growth of apical buds while stimulating the outgrowth of axillary buds.
植物的株型及后续生产力由茎尖优势决定，而硼（植物生长和繁殖必需的微量元素之一）缺乏会扰乱茎尖优势。然而，硼在硼缺乏情况下控制茎尖优势或腋芽生长的机制仍不清楚。这项工作旨在研究这一过程的机制基础，重点关注硼与生长素极性运输之间的相互作用。采用全芽表型分析方法并运用多种互补方法，我们发现硼缺乏抑制植物生长并改变株型，导致第1 - 3节位的腋芽生长。这与硼缺乏时茎尖部分芽中生长素的积累有关。施用N - 1 - 萘基邻苯二甲酰胺酸抑制生长素从茎尖的运输，促进了硼充足（+B）植株中腋芽的生长。在去顶植株中，向茎尖施用外源生长素仅抑制了+B植株中腋芽的生长。在较高生长素剂量下，在茎的下部观察到吲哚乙酸（IAA）的毒性作用，在+B植株中比在缺硼（-B）植株中更严重。此外，在 -B条件下，PsPIN3的表达显著下调。这些结果表明，硼缺乏抑制了生长素从顶芽通过主茎向植株下部的极性运输，导致顶芽中生长素水平升高，这抑制了顶芽生长，同时刺激了腋芽生长。
