Evidence of the functional role of the ethylene receptor genes SlETR4 and SlETR5 in ethylene signal transduction in tomato

Abstract

Ethylene receptors are key factors for ethylene signal transduction. In tomato, six ethylene receptor genes (SlETR1-SlETR6) have been identified. Mutations in different ethylene receptor genes result in different phenotypes that are useful for elucidating the roles of each gene. In this study, we screened mutants of two ethylene receptor genes, SLETR4 and SLETR5, from a Micro-Tom mutant library generated by TILLING. We identified two ethylene receptor mutants with altered phenotypes and named them Sletr4-1 and Sletr5-1. Sletr4-1 has a mutation between the transmembrane and GAF domains, while Sletr5-1 has a mutation within the GAF domain. Sletr4-1 showed increased hypocotyl and root lengths, compared to those of wild type plants, under ethylene exposure. Moreover, the fruit shelf life of this mutant was extended, titratable acidity was increased and total soluble solids was decreased, suggesting a reduced ethylene sensitivity. In contrast, in the absence of exogenous ethylene, the hypocotyl and root lengths of Sletr5-1 were shorter than those of the wild type, and the fruit shelf life was shorter, suggesting that these mutants have increased ethylene sensitivity. Gene expression analysis showed that SlNR was up-regulated in the Sletr5-1 mutant line, in contrast to the down-regulation observed in the Sletr4-1 mutant line, while the down regulation of SlCTR1, SlEIN2, SlEIL1, SlEIL3, and SlERF.E4 was observed in Sletr4-1 mutant allele, suggesting that these two ethylene receptors have functional roles in ethylene signalling and demonstrating, for the first time, a function of the GAF domain of ethylene receptors. These results suggest that the Sletr4-1 and Sletr5-1 mutants are useful for elucidating the complex mechanisms of ethylene signalling through the analysis of ethylene receptors in tomato.

Mutations in tomato 1‐aminocyclopropane carboxylic acid synthase2 uncover its role in development beside fruit ripening

“…Consistent with this, the tomato etr1‐1 mutant, which has reduced ethylene sensitivity, also exhibits delayed ripening progression (Okabe et al ., 2011). Similar to acs2‐2 , tomato etr4‐1 , which has reduced ethylene sensitivity, shows a delay in flowering (Mubarok et al ., 2019). Akin to contrasting phenotypes of acs2 mutants, tomato etr4‐1 fruits show higher shelf life, while etr5‐1 fruits, with increased ethylene sensitivity, show reduced shelf life (Mubarok et al ., 2019).…”

“…Similar to acs2‐2 , tomato etr4‐1 , which has reduced ethylene sensitivity, shows a delay in flowering (Mubarok et al ., 2019). Akin to contrasting phenotypes of acs2 mutants, tomato etr4‐1 fruits show higher shelf life, while etr5‐1 fruits, with increased ethylene sensitivity, show reduced shelf life (Mubarok et al ., 2019). Thus, the onset and progression of ripening of tomato fruits are affected by multiple loci modulating ethylene synthesis and/or signal transduction, wherein ACS2 also plays a pivotal role.…”

“…Likewise, overexpression of EIN3 ‐like transcription factor ( EIL1 ) restores ripening in Nr (Chen et al ., 2004), indicating the operation of normal ethylene signal transduction in the mutant. Mutations in ETR1 , ETR4 , ETR5 , and ETR7 had differential effects on tomato ripening, probably by affecting their ethylene sensitivity (Okabe et al ., 2011; Mubarok et al ., 2019; Chen et al ., 2020).…”

The Role of 1‐Methylcyclopropene in the regulation of ethylene biosynthesis and ethylene receptor gene expression in Mangifera indica L. (Mango Fruit)

“…In mango, a similar ripening pattern was found, implying a link between the expression of the ethylene receptor and the activities of ACO and ACS (Pathak et al, 2003). The increased expression of the ethylene receptor, along with the higher sensitivity and production of ethylene, was discovered in petioles of tomato (Syariful et al, 2019). Inhibition of ethylene by 1-MCP is based on the ability of 1-MCP to irreversibly bind to ethylene receptors, consequently diminishing the normal increase in ACS and ACO enzyme activities during ripening and senescence (Binder & Bleecker, 2003).…”

Data on the yield and quality of organically hybrids of tropical tomato fruits at two stages of fruit maturation

“…TA was measured using the modified titration method described by Mubarok et al. [6], [7]. Briefly, 5 g of fresh fruit was homogenised with 50 mL distilled water and then titrated up to pH 8.1 with 0.1 N sodium hydroxide.…”