A functional allele of CsFUL1 regulates fruit length through inhibiting CsSUP and auxin transport in cucumber

First author: Jianyu Zhao; Affiliations: China Agraicultural University (中国农业大学): Beijing, China

Corresponding author: Xiaolan Zhang

Fruit length is a prominent agricultural trait during cucumber domestication and diversifying selection; however, the regulatory mechanisms of fruit elongation remain elusive. We found two alleles of the FRUITFULL-like MADS-box gene CsFUL1 with 3393^C-ASNP variation among 150 cucumber lines, in which CsFUL1^A was specifically enriched in the long-fruited East Asian type cucumbers (China and Japan), whereas the CsFUL1^C allele was randomly distributed in natural cucumber populations including wild and semi-wild cucumbers. CsFUL1A knockdown led to further fruit elongation in cucumber, whereas elevated expression of CsFUL1A resulted in significantly shorter fruits. No effect on fruit elongation was detected upon modulation of CsFUL1C expression, suggesting that CsFUL1A is a gain-of-function allele in long-fruited cucumber that acts as a repressor during diversifying selection of East Asian cucumbers. Furthermore, CsFUL1A binds to the CArG box in the promoter region of the SUPERMAN (CsSUP) gene to repress its expression in regulating cell division and expansion. Additionally, CsFUL1A inhibits the expression of auxin transporters PIN-FORMED 1 and 7, resulting in decreases in auxin accumulation in fruits. Together, our work provides an agriculturally important allele with practical application for manipulation of fruit length via modulating CsFUL1A expression levels in cucumber breeding.

果实的长度是黄瓜驯化过程和多样化选择育种中一个非常重要的农艺性状。然而，目前我们对于调控黄瓜果实长度的分子机制还不清楚。本文中，作者基于150个黄瓜株系，发现在CsFUL1基因3393处存在两种SNP变异类型：C和A。其中，CsFUL1A特异性的富集于果实较长的东亚黄瓜中，而另外一个CsFUL1C则随机分布于自然的黄瓜群体中，包括野生和半野生黄瓜。敲低CsFUL1A能够导致黄瓜果实进一步的伸长，而提升CsFUL1A的表达则导致果实长度显著缩短。而对于CsFUL1C表达的调整对于黄瓜果实的长度并没有显著的影响，说明CsFUL1A是长果实黄瓜品种的功能获得性等位基因，在东亚黄瓜的多样化选择中主要作为抑制子发挥作用。此外，CsFUL1A能够结合到CsSUP基因启动子区的CArG基序上，抑制CsSUP基因的表达，从而调控细胞分裂和扩张。另外，CsFUL1A能够抑制生长素转运蛋白PIN1和PIN7的表达，进而降低生长素在果实中的积累。综上，本文的研究揭示了一个黄瓜重要的农艺等位基因，在黄瓜育种项目中可以通过调控CsFUL1A的表达水平来控制果实的长度，具有潜在的实践应用价值。

通讯：张小兰  (http://yyxy.cau.edu.cn/art/2018/2/18/art_29675_28.html)

个人简介：1995-1999年，中国农业大学，学士；1999-2002年，中国农业大学，硕士；2002-2007年，美国佐治亚大学，博士；2007- 2011年，美国加州理工大学，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/10.1105/tpc.18.00905

Journal: Plant Cell

First Published: April 12, 2019