Abstract
Tillering is an important agronomic trait essential for the yield of Triticum aestivum and the propagation of Aegilops tauschii. However, the effect of phytohormones on T. aestivum and Ae. tauschii tillering and the underlying regulatory mechanisms remain poorly understood. In the study, we found that T. aestivum and Ae. tauschii 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 T. aestivum, corresponding to 2.0-fold greater inhibition than that in Ae. tauschii (38.71%). Transcriptome analysis showed that differentially expressed genes (DEGs) in the T. aestivum 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 Ae. tauschii. 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 T. aestivum, whereas ABA levels were relatively stable in Ae. tauschii. The herbicide induced more cytokinin (CTK) accumulation in Ae. tauschii than in T. aestivum. External ABA clearly restricted tiller bud growth in both T. aestivum and Ae. tauschii, 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
Highlights
Wheat (Triticum aestivum L), one of the most important cereal crops worldwide, is severely infested by the notorious grass weed Aegilops tauschii in China, resulting in considerable yield losses (Zhang et al, 2007; Zhao et al, 2019)
The objectives of this study are to (i) evaluate the effect of 2,4-D isooctyl ester on the outgrowth of tiller buds in T. aestivum and Ae. tauschii; (ii) identify metabolic pathways and candidate genes involved in the diverse tillering sensitivities to 2,4-D isooctyl ester by transcriptomic analysis and validate the identified candidates using quantitative real-time PCR; (iii) assess the dynamics of endogenous hormone levels after 2,4D isooctyl ester spray application; and (iv) ascertain the effect of exogenous abscisic acid (ABA) and 6-benzyl aminopurine (6BA, a synthetic CTK) on tiller bud elongation in T. aestivum and Ae. tauschii based on the above results of endogenous hormone contents
At 3 D Isooctyl Ester-Regulated Tillering after treatment (DAT), the 2,4-D isooctyl ester dose required for 50% growth inhibition of tiller buds was estimated at approximately 1247.14 g a.i. ha−1 in T. aestivum and approximately 5444.74 g a.i. ha−1 in Ae. tauschii (Figure 1A), indicating that Ae. tauschii tillering was more tolerant to 2,4-D isooctyl ester than T. aestivum
Summary
Wheat (Triticum aestivum L), one of the most important cereal crops worldwide, is severely infested by the notorious grass weed Aegilops tauschii in China, resulting in considerable yield losses (Zhang et al, 2007; Zhao et al, 2019). 2,4-D Isooctyl Ester-Regulated Tillering difficulties in developing selective herbicides that can be applied to control it (Tahernezhad et al, 2010; Yu and Li, 2018). Auxin cannot enter the tiller bud, resulting in an indirect inhibitory effect on tillering (Booker et al, 2003). Tiller bud development was completely inhibited by exogenous application of IAA (Cai et al, 2018). 2,4-D isooctyl ester, a derivative of 2,4-D (a synthetic auxin), is an auxin herbicide popularly used for broadleaf weed control in some Poaceae crops, such as wheat and maize (Wu et al, 2008). Our previous study indicated that T. aestivum and Ae. tauschii are closely related genetically, they exhibit different sensitivities to 2,4-D isooctyl ester, including different effects on tillering. The mechanism underlying the different tillering responses of the two plant species to 2,4-D isooctyl ester is still not well understood
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
