Transcriptome Profiling Analysis Reveals Co-regulation of Hormone Pathways in Foxtail Millet during Sclerospora graminicola Infection.

Renjian Li,Xukai Li,Qi Zhang,Baojun Zhang,Guorong Chang,Yuanhuai Han,Yanqing Han

doi:10.3390/ijms21041226

Renjian Li, Xukai Li + Show 5 more

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https://doi.org/10.3390/ijms21041226

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Abstract

Sclerospora graminicola (Sacc.) Schroeter is a biotrophic pathogen of foxtail millet (Setaria italica) and increasingly impacts crop production. We explored the main factors for symptoms such as dwarfing of diseased plants and the “hedgehog panicle” by determining panicle characteristics of varieties infected with S. graminicola and analyzing the endogenous hormone-related genes in leaves of Jingu 21. Results indicated that different varieties infected by S. graminicola exhibited various symptoms. Transcriptome analysis revealed that the ent-copalyl diphosphate synthetase (CPS) encoded by Seita.2G144900 and ent-kaurene synthase (KS) encoded by Seita.2G144400 were up-regulated 4.7-fold and 2.8-fold, respectively. Results showed that the biosynthesis of gibberellin might be increased, but the gibberellin signal transduction pathway might be blocked. The abscisic acid (ABA) 8′-hydroxylase encoded by Seita.6G181300 was continuously up-regulated by 4.2-fold, 2.7-fold, 14.3-fold, and 12.9-fold from TG1 to TG4 stage, respectively. Seita.2G144900 and Seita.2G144400 increased 79-fold and 51-fold, respectively, at the panicle development stage, promoting the formation of a “hedgehog panicle”. Jasmonic acid-related synthesis enzymes LOX2s, AOS, and AOC were up-regulated at the early stage of infection, indicating that jasmonic acid played an essential role in early response to S. graminicola infection. The expression of YUC-related genes of the auxin synthesis was lower than that of the control at TG3 and TG4 stages, but the amidase encoded by Seita.2G313400 was up-regulated by more than 30-fold, indicating that the main biosynthesis pathway of auxin had changed. The results suggest that there was co-regulation of the hormone pathways during the infection of foxtail millet by S. graminicola.

Highlights

Downy mildew disease of foxtail millet (Setaria italica (L.) P
It is shown that the transcripts and protein levels of allene oxide synthase (AOS) are significantly higher in resistant cultivars in comparison with those in susceptible cultivars, suggesting that AOS may play an important role in the response of pearl millet to S. graminicola [4]
The results of our experiments provide insights into the potential role of endogenous hormones in “hedgehog panicle” and dwarfing symptoms in foxtail millet

Summary

Introduction

Downy mildew disease of foxtail millet (Setaria italica (L.) P. The incidence of downy mildew disease in China ranges between 20% and 30% but the infection rates of some susceptible varieties can exceed 70% in some years, and seriously affects foxtail millet yield and quality. Symptoms of this disease include rotten buds at the germination stage, downy mildew on the abaxial leaf surface known as “gray back”, decomposition of leaf mesophyll cells with only veins left as “white hairs”, and phyllody or witches’ broom as “hedgehog panicle”, as well as other morphological changes such as dwarfing, shortened internodes, and widened leaves. It is shown that the transcripts and protein levels of allene oxide synthase (AOS) are significantly higher in resistant cultivars in comparison with those in susceptible cultivars, suggesting that AOS may play an important role in the response of pearl millet to S. graminicola [4]

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