Beijing Key Laboratory of Ornamental Plants Germplasm Innovation & Molecular Breeding, National Engineering Research Center for Floriculture, Beijing Laboratory of Urban and Rural Ecological Environment, Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants of Education Ministry, School of Landscape Architecture, Beijing Forestry University, Beijing, 100083, China.
Zhejiang University, No. 866 Yuhangtang Road, Hangzhou, 310058, China.
BMC Plant Biol. 2023 Apr 15;23(1):197. doi: 10.1186/s12870-023-04201-2.
RWP-RKs are plant specific transcription factors, which are widely distributed in plants in the form of polygenic families and play key role in nitrogen absorption and utilization, and are crucial to plant growth and development. However, the genome-wide identification and function of RWP-RK in Compositae plants are widely unknown.
In this study, 101 RWP-RKs in Chrysanthemum lavandulifolium were identified and tandem repeat was an important way for the expansion of RWP-RKs in Compositae species. 101 RWP-RKs contain 38 NIN-like proteins (NLPs) and 31 RWP- RK domain proteins (RKDs), as well as 32 specific expansion members. qRT-PCR results showed that 7 ClNLPs in leaves were up-regulated at the floral transition stage, 10 ClNLPs were negatively regulated by low nitrate conditions, and 3 of them were up-regulated by optimal nitrate conditions. In addition, the flowering time of Chrysanthemum lavandulifolium was advanced under optimal nitrate conditions, the expression level of Cryptochromes (ClCRYs), phytochrome C (ClPHYC) and the floral integration genes GIGANTEA (ClGI), CONSTANS-LIKE (ClCOL1, ClCOL4, ClCOL5), FLOWERING LOCUS T (ClFT), FLOWERING LOCUS C (ClFLC), SUPPRESSOR OF OVER-EXPRESSION OF CONSTANS 1 (ClSOC1) also were up-regulated. The expression level of ClCRY1a, ClCRY1c, ClCRY2a and ClCRY2c in the vegetative growth stage induced by optimal nitrate reached the expression level induced by short-day in the reproductive growth stage, which supplemented the induction effect of short-day on the transcription level of floral-related genes in advance.
It was speculated that ClNLPs may act on the photoperiodic pathway under optimal nitrate environment, and ultimately regulate the flowering time by up-regulating the transcription level of ClCRYs. These results provide new perspective for exploring the mechanism of nitrate/nitrogen affecting flowering in higher plants.
RWP-RK 是植物特异性转录因子，以多基因家族的形式广泛存在于植物中，在氮吸收和利用中发挥关键作用，对植物的生长发育至关重要。然而，RWP-RK 在菊科植物中的全基因组鉴定和功能尚不清楚。
本研究在菊苣中鉴定了 101 个 RWP-RK，串联重复是菊科物种 RWP-RK 扩张的重要途径。101 个 RWP-RK 包含 38 个 NIN 样蛋白（NLPs）和 31 个 RWP-RK 结构域蛋白（RKDs），以及 32 个特异扩展成员。qRT-PCR 结果表明，叶片中的 7 个 ClNLPs 在花转变阶段上调，10 个 ClNLPs 受低硝酸盐条件的负调控，其中 3 个受最佳硝酸盐条件上调。此外，在最佳硝酸盐条件下，菊苣的开花时间提前，隐花色素（ClCRYs）、光敏色素 C（ClPHYC）和花整合基因 GI-GANTEA（ClGI）、CONSTANS-LIKE（ClCOL1、ClCOL4、ClCOL5）、FLOWERING LOCUS T（ClFT）、FLOWERING LOCUS C（ClFLC）、SUPPRESSOR OF OVER-EXPRESSION OF CONSTANS 1（ClSOC1）的表达水平也上调。最佳硝酸盐诱导的营养生长阶段中 ClCRY1a、ClCRY1c、ClCRY2a 和 ClCRY2c 的表达水平达到了生殖生长阶段短日照诱导的表达水平，补充了短日照对花相关基因转录水平的提前诱导作用。
推测 ClNLPs 在最佳硝酸盐环境下可能作用于光周期途径，最终通过上调 ClCRYs 的转录水平来调节开花时间。这些结果为探索硝酸盐/氮对高等植物开花的影响机制提供了新的视角。
