Abstract
Cultivating rice in wet or water direct seeding systems is simple and time and labor efficient. Rice (Oryza sativa) seeds are a unique cereal that can germinate not only when submerged, but also in anoxic conditions. Many complicated hormone signals interact in submerged seed germination. Ethylene is involved in rice coleoptile elongation, but little is known regarding the role of auxin signaling under submergence. This study demonstrated that the coleoptile is shorter and curlier when submerged with 2,3,5-triiodobenzoic acid (TIBA). In transcriptomic analysis, 3448 of the 31,860 genes were upregulated, and 4360 genes were downregulated with submergence and TIBA treatment. The Gene Ontology function classification results demonstrated that upregulated differentially expressed genes (DEGs) were mainly involved in redox, stress, and signal transduction, whereas the down-regulated DEGs were mainly involved in RNA transcription, stress, and development. Furthermore, auxin signaling involved in the carbohydrate metabolism pathway was demonstrated while using transcriptomic analysis and confirmed in a quantitative real-time polymerase chain reaction. In addition, the transcript levels of development-related genes and mitochondria-electron- transport-related genes were regulated by auxin signaling under submergence. Auxin signaling was not only involved in regulating rice coleoptile elongation and development, but also regulated secondary metabolism, carbohydrate metabolism, and mitochondria electron transport under submergence. Our results presented that auxin signaling plays an important role during rice coleoptile elongation upon the submergence condition and improving the advance of research of direct rice seeding system.
Highlights
Rice is among the most valuable cereal crops in the world
The polar auxin transport inhibitor triiodobenzoic acid (TIBA) was added to the combined submergence treatment to investigate the effect of auxin on rice coleoptile elongation under submerged conditions
The results indicated that auxin signaling is involved in rice coleoptile elongation and tropism under submerged conditions
Summary
Rice is among the most valuable cereal crops in the world. The rice coleoptile’s ability to grow in underwater environments has practical value for rice cultivation. Clarifying and establishing the regulation mechanism of submerged rice coleoptile growth is crucial for improving seed germination in paddy fields. Auxin is involved in coleoptile elongation [8] and it promotes cell division and meristem maintenance. Ion transport activity was involved in promoting the auxin-induced growth of maize coleoptile segments [12]. The phytohormone auxin is involved in regulating rice coleoptile elongation, little is known regarding the roles of auxin in coleoptile growth responses in submerged conditions. Auxin signaling played a central role in carbohydrate consumption during rice coleoptile elongation in the submerged condition. Our data provide important insight into the development of coleoptiles at the post-germination stages in the wet direct-seed system under submerged conditions
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