AUTHOR=Yu Haiyan , Cui Hailan , Chen Jingchao , Chen Pingping , Ji Meijing , Huang Songtao , Li Xiangju 

TITLE=Regulation of 2,4-D Isooctyl Ester on Triticum aestivum and Aegilops tauschii Tillering and Endogenous Phytohormonal Responses

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.642701

DOI=10.3389/fpls.2021.642701

ISSN=1664-462X

ABSTRACT=<p>Tillering is an important agronomic trait essential for the yield of <italic>Triticum aestivum</italic> and the propagation of <italic>Aegilops tauschii</italic>. However, the effect of phytohormones on <italic>T. aestivum</italic> and <italic>Ae. tauschii</italic> tillering and the underlying regulatory mechanisms remain poorly understood. In the study, we found that <italic>T. aestivum</italic> and <italic>Ae. tauschii</italic> exhibited different tillering sensitivities to the auxin herbicide 2,4-D isooctyl ester. At 3 days post-application, tiller bud growth was inhibited by 77.50% in <italic>T. aestivum</italic>, corresponding to 2.0-fold greater inhibition than that in <italic>Ae. tauschii</italic> (38.71%). Transcriptome analysis showed that differentially expressed genes (DEGs) in the <italic>T. aestivum</italic> response to 2,4-D isooctyl ester were mainly enriched in plant hormone metabolism and signal transduction pathways, but similar changes were not observed in <italic>Ae. tauschii</italic>. Among that, the auxin biosynthesis and signaling induced by 2,4-D isooctyl ester was quite different between the two species. A total of nine candidate genes involved in varied tillering responses were selected from the DEGs and validated by quantitative real-time PCR. Endogenous hormone levels were assayed to further verify the RNA-seq results. After 2,4-D isooctyl ester treatment, a significant increase in abscisic acid (ABA) levels was observed in <italic>T. aestivum</italic>, whereas ABA levels were relatively stable in <italic>Ae. tauschii</italic>. The herbicide induced more cytokinin (CTK) accumulation in <italic>Ae. tauschii</italic> than in <italic>T. aestivum</italic>. External ABA clearly restricted tiller bud growth in both <italic>T. aestivum</italic> and <italic>Ae. tauschii</italic>, while 6-benzyl aminopurine had no significant effect. These results indicate that ABA and CTK may be related with 2,4-D isooctyl ester-regulated tillering differences between the two species, which will help to further understand the mechanism of the auxin-mediated regulation of tillering</p>