Abstract

The number of flowers and seed-bearing structures formed by the inflorescence meristem and the formation of ovules in the female reproductive part of the flowers are important yield-related traits of crop plants. It has been shown that cytokinin is a pivotal factor regulating these traits. Here, we explore the impact of mutation of CYTOKININ OXIDASE/DEHYDROGENASE (CKX) genes encoding cytokinin-degrading enzymes on these yield-related traits in oilseed rape (Brassica napus L.). We describe the identification of four BnCKX3 and two BnCKX5 genes as regulators of reproductive development in the allotetraploid B. napus. RNA-seq analysis and in situ hybridization showed expression of these genes in reproductive organs. Loss-of-function mutants for each of these CKX gene copies were identified by targeting induced local lesions in genomes (TILLING) and combined by crossing. Sextuple ckx3 ckx5 mutants showed an increased cytokinin concentration and larger and more active inflorescence meristems. They also produced up to 72% more flowers with gynoecia containing 32% more ovules and up to 54% more pods on the main stem. The weight of seeds harvested from the main stem of plants grown in the greenhouse or in the field was increased by 20–32%. Our results show that cytokinin regulates inflorescence meristem and placenta activity in oilseed rape. The work demonstrates the potential to achieve yield enhancement in a dicot crop plant by modulating the cytokinin status through mutagenesis of specific CKX genes.

中文翻译：

---

细胞分裂素调节油菜中花序分生组织的活性和种子产量的组成部分。

摘要

花序分生组织形成的花朵数量和种子结构以及花朵的雌性生殖部分的胚珠的形成是重要的与作物产量相关的性状。已经表明细胞分裂素是调节这些特征的关键因素。在这里，我们探讨的突变的影响细胞分裂素氧化/脱氢酶（CKX编码在油菜（这些产量相关性状的细胞分裂素降解酶）的基因油菜L.）。我们描述了鉴定四个BnCKX3和两个BnCKX5基因作为异源二倍体甘蓝型油菜生殖发育的调节剂。RNA-seq分析和原位杂交显示这些基因在生殖器官中表达。通过靶向基因组中诱导的局部病变（TILLING）鉴定这些CKX基因拷贝的功能丧失突变体，并通过杂交进行组合。六元组ckx3 ckx5突变体显示增加的细胞分裂素浓度和更大，更活跃的花序分生组织。他们还产生了多达72％的花朵，其中绞股蓝含有32％的胚珠，主茎上的豆荚多达54％。从温室或田间生长的植物主要茎上收获的种子重量增加了20％至32％。我们的结果表明，细胞分裂素调节油菜的花序分生组织和胎盘活性。这项工作证明了通过诱变特定CKX基因调节细胞分裂素状态，在双子叶植物作物中实现增产的潜力。