Suppressing Type 2C Protein Phosphatases Alters Fruit Ripening and the Stress Response in Tomato

Abstract

Although ABA signaling has been widely studied in Arabidopsis, the roles of core ABA signaling components in fruit remain poorly understood. Herein, we characterize SlPP2C1, a group A type 2C protein phosphatase that negatively regulates ABA signaling and fruit ripening in tomato. The SlPP2C1 protein was localized in the cytoplasm close to AtAHG3/AtPP2CA. The SlPP2C1 gene was expressed in all tomato tissues throughout development, particularly in flowers and fruits, and it was up-regulated by dehydration and ABA treatment. SlPP2C1 expression in fruits was increased at 30 d after full bloom and peaked at the B + 1 stage. Suppression of SlPP2C1 expression significantly accelerated fruit ripening which was associated with higher levels of ABA signaling genes that are reported to alter the expression of fruit ripening genes involved in ethylene release and cell wall catabolism. SlPP2C1-RNAi (RNA interference) led to increased endogenous ABA accumulation and advanced release of ethylene in transgenic fruits compared with wild-type (WT) fruits. SlPP2C1-RNAi also resulted in abnormal flowers and obstructed the normal abscission of pedicels. SlPP2C1-RNAi plants were hypersensitized to ABA, and displayed delayed seed germination and primary root growth, and increased resistance to drought stress compared with WT plants. These results demonstrated that SlPP2C1 is a functional component in the ABA signaling pathway which participates in fruit ripening, ABA responses and drought tolerance.

Transcriptional regulatory networks controlling taste and aroma quality of apricot (Prunus armeniaca L.) fruit during ripening

“…Here, the expression of NCED1 , which is involved in ABA biosynthesis, was highly up-regulated during ripening, suggesting that ABA biosynthesis and signal transduction was induced. In tomato, SlPP2C1-RNAi led to increased endogenous ABA accumulation and significantly accelerated fruit ripening and altered the expression of fruit ripening genes involved in ethylene release and cell wall catabolism [34]. In our study, PP2C11 , PP2C27 , PP2C33 , SnRK2 were down-regulated and ABF2 was up-regulated during ripening, indicating that the PYR1-PP2C-SnRK2 pathway was activated, consistent with previous studies [21].…”

“…The plant hormone ethylene plays a major role in the ripening and quality formation of climacteric fruit [34]. In this work, we observed that the expression of an ACS2 and an ACO1 , families of which are central ethylene biosynthesis, were significantly up-regulated during ripening, while the expression of ETR , an ethylene receptor, decreased significantly.…”

“…We identified an ERF interaction factor, MYB98 , which may regulate flavor formation in apricot. ABA has been well documented to play a central role in the ripening of non-climacteric fruit, however, its regulation role underlying ripening of climacteric fruit is becoming clear [34]. Exogenous ABA has also been shown to accelerate the maturation of apricot [39].…”

Manipulation of β‐carotene levels in tomato fruits results in increased ABA content and extended shelf life

“…In contrast, silencing of three CYP707A2 isoforms, encoding ABA 8 0 -hydroxylases acting in ABA catabolism, or of ABA uridine diphosphate glucosyltransferase (SlUGT75C1), which produces esterified ABA-glucose, generated over-ripe fruits with increased ABA levels (Ji et al, 2014;Sun et al, 2017). A similar phenotype was observed in RNAi lines for SlPP2C1, a group A type 2C protein phosphatase involved in ABA signalling (Zhang et al, 2018). These observations suggest that ABA influences fruit ripening in different ways, depending on the mode (external or endogenous) and timing of the application.…”

Evolution of Abscisic Acid Signaling Module and Its Perception

“…In Arabidopsis, PP2Cs interacts with SnRK2s and inhibits the kinase activity as it dephosphorylates key serine residues in the kinase activation loop, and physically blocking the kinase catalytic site (Belin et al, 2006;Vlad et al, 2009;Soon et al, 2012). In angiosperms, group A PP2C contains multi-genes with redundant function (Leung et al, 1994;Meyer et al, 1994;Leung et al, 1997;Rodriguez et al, 1998;Saez et al, 2004;Schweighofer et al, 2004;Xue et al, 2008;Zhang et al, 2018;Fujioka et al, 2019). High-order of loss-of-function Arabidopsis mutant of PP2C displays an increase of ABA sensitivity, and partially constitutive ABA response (Saez et al, 2006;Rubio et al, 2009).…”