AUTHOR=Yang Shuang , Zhang Tianqi , Wang Ze , Zhao Xiaofei , Li Rui , Li Jing 

TITLE=Nitrilases NIT1/2/3 Positively Regulate Flowering by Inhibiting MAF4 Expression in Arabidopsis

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.889460

DOI=10.3389/fpls.2022.889460

ISSN=1664-462X

ABSTRACT=<p>Three of the nitrilases (NITs), NIT1, NIT2, and NIT3, are ubiquitously existing in plant kingdom, which catalyze indole-3-acetonitrile into the most important auxin indole-3-acetic acid. Auxin is an indispensable hormone, which plays the important roles in almost all processes of plant growth and development. However, there are few reports on the regulation of flowering-time mediated by auxin. Here, we found that in Arabidopsis, <italic>nit1/2/3</italic> showed a late flowering phenotype in short days. To explore the molecular mechanism by which NIT1/2/3 regulate flowering time, we performed transcriptome sequencing of <italic>nit1/2/3</italic>. The results showed that the expression of a MADS-box transcription factor gene <italic>MADS AFFECTING FLOWERING4</italic> (<italic>MAF4</italic>) was dramatically increased in <italic>nit1/2/3</italic> comparing to wild type (WT). MAF4 is one of the paralogs of the potent flowering inhibitor FLOWERING LOCUS C (FLC). There are four other paralogs in FLC clade in Arabidopsis, including FLOWERING LOCUS M (FLM/MAF1), MAF2, MAF3, and MAF5. The late flowering phenotype of <italic>nit1/2/3</italic> could not be observed in the <italic>maf4</italic> background, indicating that the phenotype was specifically dependent on MAF4 rather than other FLC clade members. Interestingly, the expression of a lncRNA gene <italic>MAS</italic>, which is transcribed in the opposite direction of <italic>MAF4</italic>, was found significantly increased in <italic>nit1/2/3</italic>. Also, <italic>MAS</italic> has been reported to activate <italic>MAF4</italic> transcription by promoting histone 3 lysine 4 trimethylation (H3K4me3). As expected, H3K4me3 deposition at <italic>MAF4</italic> locus in <italic>nit1/2/3</italic> was highly enriched and significantly higher than that of WT. In summary, we show that NITs, NIT1/2/3, positively regulate flowering by repressing <italic>MAF4</italic> through manipulating H3K4me3 modification. Further study needs to be performed to explore the largely unknown mechanisms behind it.</p>