Abstract
Copper deficiency reduces plant growth, male fertility, and seed set. The contribution of copper to female fertility and the underlying molecular aspects of copper deficiency‐caused phenotypes are not well known. We show that among copper deficiency‐caused defects in Arabidopsis thaliana were also the increased shoot branching, delayed flowering and senescence, and entirely abolished gynoecium fertility. The increased shoot branching of copper‐deficient plants was rescued by the exogenous application of auxin or copper. The delayed flowering was associated with the decreased expression of the floral activator, FT. Copper deficiency also decreased the expression of senescence‐associated genes, WRKY53 and SAG13, but increased the expression of SAG12. The reduced fertility of copper‐deficient plants stemmed from multiple factors including the abnormal stigma papillae development, the abolished gynoecium fertility, and the failure of anthers to dehisce. The latter defect was associated with reduced lignification, the upregulation of copper microRNAs and the downregulation of their targets, laccases, implicated in lignin synthesis. Copper‐deficient plants accumulated ROS in pollen and had reduced cytochrome c oxidase activity in both leaves and floral buds. This study opens new avenues for the investigation into the relationship between copper homeostasis, hormone‐mediated shoot architecture, gynoecium fertility, and copper deficiency‐derived nutritional signals leading to the delay in flowering and senescence.
Highlights
It has been known for decades that deficiency in the micronutrient copper in alkaline soils compromises plant fertility with the most negative impact on wheat grain production (Broadley et al, 2012; Graham, 1978; Graves and Sutcliffe, 1974; Shorrocks and Alloway, 1988; Solberg et al, 1999)
Copper deficiency increases shoot branching that can be rescued by auxin We first tested the effect of different copper concentrations on the growth and development of A. thaliana because this has not been done comprehensively
We noted that apical flower bud on the primary inflorescence was aborted in plants grown under copper deficiency (Fig. 1C-I, II), suggesting that increased branching might be related to the removal of auxin-dependent apical dominance
Summary
It has been known for decades that deficiency in the micronutrient copper in alkaline soils compromises plant fertility with the most negative impact on wheat grain production (Broadley et al, 2012; Graham, 1978; Graves and Sutcliffe, 1974; Shorrocks and Alloway, 1988; Solberg et al, 1999). We tested whether the late flowering time is caused by the delayed vegetative-to-reproductive stage transition or the slower growth rates of plants under copper deficiency. The number of floral buds on the primary inflorescence upon transition to flowering was significantly reduced in copper-deficient plants (Fig. 2C).
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