CUP SHAPED COTYLEDON1 (CUC1) and CUC2 Regulate Cytokinin Homeostasis to Determine Ovule Number

First author: Mara Cucinotta; Affiliations: Università degli Studi di Milano (米兰大学): Milano, Italy

Corresponding author: Lucia Colombo

Seeds derive from ovules (胚珠) upon fertilization. Therefore, the total number of ovules determines the final seed yield, a fundamental trait in crop plants. Among the factors that coordinate the process of ovule formation, the transcription factors CUP SHAPED COTYLEDON 1 (CUC1) and CUC2 and the hormone cytokinin (CK) have a particularly prominent role. Indeed, the absence of both CUC1 and CUC2 causes a severe reduction in ovule number, a phenotype that can be rescued by CK treatment. In this work, we combined CK quantification with an integrative genome-wide target identification approach, to select genes regulated by CUCs that are also involved in CK metabolism. We focused our attention on the functional characterization of UDP-GLUCOSYL TRANSFERASE 85A3 (UGT85A3) and UGT73C1, which are up-regulated in the absence of CUC1 and CUC2 and encode enzymes able to catalyse CK inactivation by O-glucosylation. Our results demonstrate a role for these UGTs as a link between CUCs and CK homeostasis, and underpin the importance of CUCs and CKs in seed yield determination.

植物胚珠受精作用后会发育成为种子。因此，胚珠的数量直接决定了最终种子的产量，而种子产量是作物的一个最重要指标。在众多参与胚珠形成调控的因素中，转录因子CUC1和CUC2及植物激素细胞分裂素CK显得尤其重要。确实，CUC1和CUC2功能缺失突变体会导致胚珠数量的急剧减少，而通过CK处理能够恢复这种突变体的表型。本文通过结合CK定量及全集因子范围的靶标鉴定方法，筛选那些受到CUC蛋白调控而且参与CK代谢的基因。作者重点功能鉴定了UGT85A3和UGT73C1两个基因，这两个基因在CUC1和CUC2缺失突变体中表达量上调，并且编码的酶能够通过氧-葡糖基化催化CK失活。本文的研究揭示了UGT基因作为CUC和CK内稳态之间的中间纽带，并且表明了CUC和CK在种子产量方面的重要性。

doi: https://doi.org/10.1093/jxb/ery281

Journal: Journal of Experimental Botany

Published date: 26 July, 2018

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