AUTHOR=Li Jingrui , Fan Mi , Zhang Qinqin , Lü Guiyun , Wu Xiaolei , Gong Binbin , Wang Yubo , Zhang Ying , Gao Hongbo TITLE=Transcriptome analysis reveals that auxin promotes strigolactone-induced adventitious root growth in the hypocotyl of melon seedlings JOURNAL=Frontiers in Plant Science VOLUME=Volume 14 - 2023 YEAR=2023 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1192340 DOI=10.3389/fpls.2023.1192340 ISSN=1664-462X ABSTRACT=Introduction

Strigolactone (SL) and auxin are two important phytohormones involved in plant root development, but whether they show synergistic or mutual promotion effects during adventitious root (AR) formation has not been adequately explored.

Methods

In this study, we investigated the mechanisms of GR24 (synthetic SL) and indole-3-acetic acid (IAA; a type of auxin) in the formation of ARs using melon as the study material.

Results

Morphological measurements showed that the AR number, length, superficial area, and volume under the GR24 treatment were 1.60–3.27, 1.58–3.99, 2.06–3.42, and 3.00–6.11 times greater than those of the control group, respectively, at 6–10 days; the GR24+IAA treatment further promoted AR formation in melon seedlings, and the AR number, length, superficial area, and volume under the GR24+IAA treatment were 1.44–1.51, 1.28–1.73, 1.19–1.83, and 1.31–1.87 times greater than those obtained with the GR24 treatment, respectively. Transcriptome analysis revealed 2,742, 3,352, and 2,321 differentially expressed genes (DEGs) identified from the GR24 vs. control, GR24+IAA vs. control, and GR24+IAA vs. GR24 comparisons, respectively. The GR24 treatment and GR24+IAA treatment affected auxin and SL synthesis as well as components of the phytohormone signal transduction pathway, such as auxin, brassinosteroid (BR), ethylene (ETH), cytokinin (CK), gibberellin (GA), and abscisic acid (ABA). The concentrations of auxin, GA, zeatin (ZT), and ABA were evaluated using high-performance liquid chromatography (HPLC). From 6 to 10 days, the auxin, GA, and ZT contents in the GR24 treatment group were increased by 11.48%–15.34%, 11.83%–19.50%, and 22.52%–66.17%, respectively, compared to the control group, and these features were increased by 22.00%–31.20%, 21.29%–25.75%, 51.76%–98.96%, respectively, in the GR24+IAA treatment group compared with the control group. Compared to that in the control, the ABA content decreased by 10.30%–11.83% in the GR24 treatment group and decreased by 18.78%-24.00% in the GR24+IAA treatment group at 6–10 days.

Discussion

Our study revealed an interaction between strigolactone and auxin in the induction of AR formation in melon seedlings by affecting the expression of genes related to plant hormone pathways and contents.