Dynamic transcriptome and phytohormone profiling along the time of light exposure in the mesocotyl of rice seedling

Abstract

Mesocotyl elongation is an important trait influencing seedling emergence and establishment in rice direct-seeding cultivation and is immediately inhibited after light exposure. Detailed researches on the molecular basis and biological processes underlying light repression of mesocotyl growth could probably provide useful information for key factors controlling this trait. Here we monitored the transcriptome and endogenous phytohormone changes specifically in the elongating mesocotyl in response to light exposure with a time-course. It was revealed that 974 transcripts were significantly differentially expressed (FDR < 0.05, |log2 (L/D) | ≥2) after light exposure. Most of the differential expression genes associated with the responses to hormone. Metabolic pathway analysis using the KEGG system suggested plant hormone signal transduction, α-linolenic acid metabolism and diterpenoid biosynthesis were critical processes of mesocotyl growth inhibited by light. Consistent with DEGs, the endogenous IAA, tZ and GA3 content was significantly reduced while JA level was dramatically increased, which indicated that light inhibited rice mesocotyl growth through decreasing IAA, tZ and GA3 content and/or increasing JA level. The present results enriched our knowledge about the genes and phytohormones regulating mesocotyl elongation in rice, which may help improve future studies on associated genes and develop new varieties tolerance to deep sowing.

Mesocotyl elongation, an essential trait for dry-seeded rice (Oryza sativa L.): a review of physiological and genetic basis

“…IAA could promote rice mesocotyl elongation by 0.027 cm, 0.052 cm, and 0.085 cm under the concentration of 0.5 µL/L, 1 µL/L, and 2 µL/L, respectively (Cao et al 2005). Feng et al (2017) also reported that the exogenous IAA could promote mesocotyl elongation of etiolated rice seedlings for 2 days after germination in darkness. Feng et al (2017) observed that the level of IAA was decreased under light treatment, and the change was consisting with the down-expression of auxin signaling genes OsSAUR24 and OsGH3.1.…”

“…Feng et al (2017) also reported that the exogenous IAA could promote mesocotyl elongation of etiolated rice seedlings for 2 days after germination in darkness. Feng et al (2017) observed that the level of IAA was decreased under light treatment, and the change was consisting with the down-expression of auxin signaling genes OsSAUR24 and OsGH3.1. Moreover, there is a relationship on mesocotyl elongation between ethylene and high temperature.…”

“…Whereas, elongated mesocotyl mutant seedlings displayed a disruption in de-etiolation responses under red and far-red light conditions, with an apparent elongation of mesocotyl (Shi et al 2013). Furthermore, mesocotyl elongation is inhibited after light exposure due to the dynamic changes of endogenous phytohormone, which mainly include the decreases of IAA, trans-zeatin (tZ), and GA 3 contents or the increase of JA level (Feng et al 2017). Study on maize mesocotyl showed that the activity of polyamine oxidase (PAO) was enhanced after light exposure, then after the oxidative decomposition of polyamines (Pas), H 2 O 2 was produced.…”

Genome-Wide Association Study (GWAS) for Mesocotyl Elongation in Rice (Oryza sativa L.) under Multiple Culture Conditions

“…The elongation of mesocotyl was influenced by various environmental factors, such as light, temperature, moisture [28,29]. Thus, rice mesocotyl elongation were varied among different culture media, such as soil [26], sand [17], water [30].…”

Integrated analyses of rice dark response and leaf color regulation reveal links with porphyrin and chlorophyll metabolism

“…It has been observed that middle mesocotyl elongation was almost completely inhibited when germinating seeds were exposed to low-intensity light. RNA-Seq analysis revealed that most of the differential expressed genes (DEGs) were associated with hormone changes that occur in response to light exposure (Feng et al, 2017). Comparative transcriptome pro ling for low-light tolerant and sensitive rice varieties was carried out via RNA-Seq analysis, and DEGs induced by low-intensity light at the tillering stage were identi ed (Sekhar et al, 2019).…”