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

Abstract

SUMMARY The role of ethylene in plant development is mostly inferred from its exogenous application. The usage of mutants affecting ethylene biosynthesis proffers a better alternative to decipher its role. In tomato (Solanum lycopersicum), 1‐aminocyclopropane carboxylic acid synthase2 (ACS2) is a key enzyme regulating ripening‐specific ethylene biosynthesis. We characterised two contrasting acs2 mutants; acs2‐1 overproduces ethylene, has higher ACS activity, and has increased protein levels, while acs2‐2 is an ethylene underproducer, displays lower ACS activity, and has lower protein levels than wild type. Consistent with high/low ethylene emission, the mutants show opposite phenotypes, physiological responses, and metabolomic profiles compared with the wild type. The acs2‐1 mutant shows early seed germination, faster leaf senescence, and accelerated fruit ripening. Conversely, acs2‐2 has delayed seed germination, slower leaf senescence, and prolonged fruit ripening. The phytohormone profiles of mutants were mostly opposite in the leaves and fruits. The faster/slower senescence of acs2‐1/acs2‐2 leaves correlated with the endogenous ethylene/zeatin ratio. The genetic analysis showed that the metabolite profiles of respective mutants co‐segregated with the homozygous mutant progeny. Our results uncover that besides ripening, ACS2 participates in the vegetative and reproductive development of tomato. The distinct influence of ethylene on phytohormone profiles indicates the intertwining of ethylene action with other phytohormones in regulating plant development.

Seeing the unseen: A trifoliate (MYB117) mutant allele fortifies folate and carotenoids in tomato fruits

“…The metabolic shifts are considered as a penultimate manifestation of homeostasis alteration at the systems level. Corresponding with phenotypic alteration, the metabolome profile of tf-5 was markedly different from WT, a feature seen with ripening-related TFs (Osorio et al, 2011), or hormonal mutants (Sharma et al, 2021). A distinctive feature of the shift was higher amino acid levels in tf-5 .…”

“…AV) were used ( Table S1 ). The tf-5 mutant was isolated from the EMS-mutagenized AV M 2 population (Sharma et al, 2021) and was used in BC 2 F 2 generation and its progeny. Based on similarity to trifoliate mutants (Naz et al, 2013), the MYB117 gene (Solyc05g007870) of tf-5 was sequenced and designated as a new tf-5 allele.…”

The new kid on the block: a dominant‐negative mutation of phototropin1 enhances carotenoid content in tomato fruits

“…On the contrary, in Nps1* though auxin level is high and ethylene emission is reduced, fruits accumulate a high amount of carotenoids. Though total suppression of ethylene biosynthesis reduces carotenoids in tomato fruits (Oeller et al, 1991;Lanahan et al, 1994), reduced ethylene emission does not lead to reduced carotenoids, as seen in Nps1* and other tomato mutants (Kilambi et al, 2013;Sharma et al, 2020). The role of other hormones in increasing carotenoid levels in Nps1* is also equivocal.…”

“…Similar to Nps1*, an auxin-resistant (Balbi and Lomax, 2003) and a NO-overproducing mutant (Bodanapu et al, 2016) show prolonged pre-MG phase implying hormonal participation. In tomato fruits, enhanced ethylene emission coupled with high ABA and low IAA levels accelerated the attainment of MG (Liang et al, 2020;Sharma et al, 2020). Conversely, reduced ABA, ethylene levels, and high auxin levels may delay the transition to MG in Nps1*.…”

“…Sugar content, pH and firmness of fruits were determined as described by Gupta et al (2014). The respiration rate of tomato fruits was measured as described by Sharma et al (2020).…”