Integrated Signals of Jasmonates, Sugars, Cytokinins and Auxin Influence the Initial Growth of the Second Buds of Chrysanthemum after Decapitation.

Daojin Sun,Peiling Li,Jiali Zhang,Qi Yu,Luyao Zhang,Fadi Chen,Aiping Song,Yu Zhang,Weimin Fang,Xiaojuan Xing,Lian Ding

doi:10.3390/biology10050440

Abstract

Simple SummaryWe sequenced the first third-generation transcriptome of chrysanthemum and analyzed the factors involved in the outgrowth of the second buds after decapitation. In addition to classic hormones (auxin, cytokinins, and strigolactone), jasmonates and sugars were also found to be involved in this process, which might be related to the initiation of dormant buds.Decapitation is common in horticulture for altering plant architecture. The decapitation of chrysanthemum plants breaks apical dominance and leads to more flowers on lateral branches, resulting in landscape flowers with good coverage. We performed both third- and second-generation transcriptome sequencing of the second buds of chrysanthemum. This third-generation transcriptome is the first sequenced third-generation transcriptome of chrysanthemum, revealing alternative splicing events, lncRNAs, and transcription factors. Aside from the classic hormones, the expression of jasmonate-related genes changed because of this process. Sugars also played an important role in this process, with upregulated expression of sucrose transport-related and TPS genes. We constructed a model of the initial growth of the second buds after decapitation. Auxin export and sugar influx activated the growth of these buds, while the JA-Ile caused by wounding inhibited the expression of CycD genes from 0 h to 6 h. After wound recovery, cytokinins accumulated in the second buds and might have induced ARR12 expression to upregulate CycD gene expression from 6 h to 48 h, together with sugars. Therefore, jasmonates, cytokinins, sugars, and auxin work together to determine the fate of the buds of plants with short internodes, such as chrysanthemum.

Highlights

Control of plant architecture is one of the most sought-after objectives of breeders, with the green revolution having provided enormous economic value since the 1960s–1970s [1,2]
third-generation sequencing (TGS) has the advantage of generating long reads, but it succumbs to a relatively high error rate, which can be corrected by self-correction via circular consensus reads and next-generation sequencing (NGS) data
Lateral buds are repressed by apical buds through weaker sugar absorption and lower capacity to export indoleacetic acid (IAA) to polar auxin transport stream (PATS) (Figure 5a)

Summary

Introduction

Control of plant architecture is one of the most sought-after objectives of breeders, with the green revolution having provided enormous economic value since the 1960s–1970s [1,2]. The number, length, and angle of the lateral branches of plants determine plant architecture [3]. Shoot branching involves multiple complex biological processes that can be divided into two main processes: bud initiation and bud outgrowth [3]. The axillary meristem arises in the axils of leaves along the primary shoot axis and produces several leaves that form buds. These buds can develop into vegetative branches or can remain dormant. All buds have the potential to grow into branches, but not all buds have the opportunity to grow and develop, due to the limited resources provided for the plant lifecycle, so plant architecture is mostly regulated by the process of bud outgrowth [4]. Endogenous, developmental, and environmental factors work together to determine the fate of buds; whether to break dormancy or not [5]

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