CsSPL functions as an adaptor between HD-ZIP III and CsWUS transcription factors regulating anther and ovule development in Cucumis sativus (cucumber)

First author: Xiaofeng Liu; Affiliations: China Agricultural University (中国农业大学): Beijing, China

Corresponding author: Xiaolan Zhang (张小兰)

Anther and ovule genesis (起源，发生) preconditions crop fertilization and fruit production; however, coordinative regulation of anther and ovule development and underlying molecular pathways remain largely elusive. Here, we found that SPOROCYTELESS (SPL)/NOZZLE (NZZ) expression was nearly abolished in a Cucumis sativus (cucumber; 黄瓜) mutant with severely defective anther and ovule development. CsSPL was expressed specifically in the developing anthers and ovules. Knock-down of CsSPL reduced male and female fertility with malformed pollen (畸形花粉) and suppressed ovule development. Importantly, CsSPL directly interacted with CsWUS (WUSCHEL) in the nucellus and YABBY family genes in integuments (珠被), and positively regulated CsWUS expression, meanwhile the HD-ZIP III gene CsPHB (PHABULOSA), expressed specifically in the nucellus, promoted CsSPL expression by binding to the CsSPL promoter. Thus, CsSPL acts as an adaptor to link CsPHB and CsWUS functioning, underpinning a previously unidentified regulatory pathway orchestrating sex organ development in planta. In addition, auxin accumulation was reduced in the reproductive organs of CsSPL knock-down plants. Biochemical analyses further showed that CsSPL stimulated the expression of AUXIN RESPONSE FACTOR 3 (CsARF3), and was positively regulated by CsARF13 during reproductive organ development, indicating sequential interactions of CsSPL with auxin signaling components in orchestrating anther and ovule development.

花药和胚珠发生是作物受精和果实产量的先决条件，然而目前对于花药和胚珠的协调调控及底层的分子调控通路仍然不是了解得很清楚。本文发现在黄瓜花药和胚珠发育缺陷的突变体中，SPL/NZZ基因的正常表达遭到破坏。CsSPL基因特异在黄瓜花药和胚珠发育过程中表达。敲低CsSPL基因的表达会降低雄性和雌性的育性，同时产生畸形花粉，抑制胚珠的发育。重要的是CsSPL会直接与CsWUS蛋白在核内互作，还能与YABBY家族的基因在珠被中互作，并正向调控CsWUS基因的表达。另外，黄瓜中HD-ZIP III基因CsPHB特异在核中表达，并通过结合到CsSPL的启动子促进CsSPL基因的表达。因此，CsSPL作为一个链接CsPHB和CsWUS的中间体发挥作用，这构成了先前植物中未鉴定的性器官发育相关调控通路的基础。另外，在CsSPL敲低植株中的生长素积累减少。生化分析进一步显示CsSPL会刺激生长素响应因子CsARF3基因的表达，并且在生殖器官发育过程中被CsARF13蛋白正向调控，揭示了CsSPL与生长素信号通路组分的互作作用于植物花药的胚珠的发育。

通讯：张小兰 (http://nxy.cau.edu.cn/art/2012/4/24/art_665_113146.html)

个人简介：1995-1999年，中国农业大学，蔬菜系，学士；1999-2002年，中国农业大学，蔬菜系，硕士；2002-2007年，美国佐治亚大学，植物生物系，博士；2007-2011年，美国加州理工大学，生物系，博士后。

研究方向：蔬菜花和果实发育的分子机理；黄瓜性别决定的分子机制；黄瓜果刺的起始与膨大的基因调控网络。

doi: https://doi.org/10.1111/tpj.13877

Journal: the plant journal

First Published date: 31 March, 2018

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