The tomato ethylene receptors NR and LeETR4 are negative regulators of ethylene response and exhibit functional compensation within a multigene family

Abstract

The plant hormone ethylene is involved in many developmental processes, including fruit ripening, abscission, senescence, and leaf epinasty. Tomato contains a family of ethylene receptors, designated LeETR1, LeETR2, NR, LeETR4, and LeETR5, with homology to the Arabidopsis ETR1 ethylene receptor. Transgenic plants with reduced LeETR4 gene expression display multiple symptoms of extreme ethylene sensitivity, including severe epinasty, enhanced flower senescence, and accelerated fruit ripening. Therefore, LeETR4 is a negative regulator of ethylene responses. Reduced expression of this single gene affects multiple developmental processes in tomato, whereas in Arabidopsis multiple ethylene receptors must be inactivated to increase ethylene response. Transgenic lines with reduced NR mRNA levels exhibit normal ethylene sensitivity but elevated levels of LeETR4 mRNA, indicating a functional compensation of LeETR4 for reduced NR expression. Overexpression of NR in lines with lowered LeETR4 gene expression eliminates the ethylene-sensitive phenotype, indicating that despite marked differences in structure these ethylene receptors are functionally redundant.

Response to Xanthomonas campestris pv.vesicatoria in Tomato Involves Regulation of Ethylene Receptor Gene Expression

“…In tomato, five different members of an ethylene receptor gene family, LeETR1, LeETR2, NR, LeETR4, and LeETR5, have been isolated. In transgenic tomato plants, reduced expression of one of these receptor genes, LeETR4, also resulted in constitutive ethylene responses such as leaf epinasty and flower senescence, indicating that a reduction in receptor level causes an increase in ethylene sensitivity (Tieman et al, 2000). Although the effect of increasing ethylene receptor levels has not been reported previously, the evidence cited above suggests that an increase in receptors would reduce sensitivity.…”

“…Similarly, decreased LeETR4 expression in antisense tomato lines caused constitutive ethylene responses such as leaf epinasty and accelerated flower senescence (Tieman et al, 2000). Therefore, a reduction in ethylene receptor levels increases sensitivity to ethylene.…”

Genome sequence of the hot pepper provides insights into the evolution of pungency in Capsicum species

“…The hot pepper genome contained 636 non-TIR (Toll/interleukin-1 receptor)-type NBS-LRRs, a number significantly higher than the 525 non-TIR NBS-LRRs in rice 40 . The number of TIR-type proteins in the hot pepper genome (48) was similar to that in potato (47) (Supplementary Table 39). More than half of the NBS-LRR subclasses in each Solanaceae genome were classified into 37 subclasses (Supplementary Table 41).…”

“…44) and NOR 45 ) and genes involved in ethylene signaling pathways (NR 46 , ETR4 (ref. 47), EIN2 (ref. 48) and EIL families 49 ) was conserved during fruit ripening (Fig.…”

Phytochrome RNAi enhances major fibre quality and agronomic traits of the cotton Gossypium hirsutum L

“…In light-grown tissues from a sorghum phyB mutant, PHYA expression was increased in all light conditions tested 19 . These cross-regulatory effects may be the manifestations of a compensatory regulatory network [20][21][22] . In cotton, we observed a substantial increase in PHYB transcript in the strongest of our T 3 -1_7 RNAi line (Fig.…”