ABA-responsive AREB1/ABI3-1/ABI5 cascade regulates IAA oxidase gene SlDAO2 to inhibit hypocotyl elongation in tomato

Genome-Wide Analysis of the Phospholipase Ds in Perennial Ryegrass Highlights LpABFs-LpPLDδ3 Cascade Modulated Osmotic and Heat Stress Responses

The phospholipase Ds (PLDs) are crucial for cellular signalling and play roles in plant abiotic stress response. In this study, we identified 12 PLD genes from the genome data of perennial ryegrass (Lolium perenne), which is widely used as forage and turfgrass. Among them, LpPLDδ3 was significantly repressed by ABA treatment, and induced by drought stress and heat stress treatments. The ectopic overexpression (OE) of LpPLDδ3 in Arabidopsis enhanced plant tolerance to osmotic and heat stress as demonstrated by an increased survival rate and reduced malondialdehyde (MDA) accumulation and electrolyte leakage (EL). Arabidopsis endogenous ABA RESPONSIVE ELEMENT BINDING FACTORs (ABFs) and heat stress responsive genes were elevated in LpPLDδ3 OE lines under osmotic and heat stress treatments. Additionally, overexpression of LpPLDδ3 in perennial ryegrass protoplasts could increase heat stress tolerance and elevate expression level of heat stress responsive genes. Moreover, LpABF2 and LpABF4 depressed the LpPLDδ3 expression by directly binding to its ABRE core-binding motif of promoter region. In summary, LpPLDδ3 was repressed by LpABF2 and LpABF4 and positively involved in perennial ryegrass osmotic and heat stress responses.

The MdIAA29-MdARF4 complex plays an important role in balancing plant height with salt and drought stress responses

Breeding dwarf apple (Malus domestica) varieties is a recent trend in agriculture because such varieties are easy to maintain and have high yields; however, dwarf apple trees generally have poor stress tolerance. Balancing apple plant height and stress response has been an important breeding goal. In this study, aux/indole-3-acetic acid 29 gene in apple (MdIAA29) overexpression lines (#1, #2, and #3) had reduced plant height by 39%, 31%, and 35%, respectively, suitable for close planting applications. Surprisingly, the dwarf MdIAA29-overexpressing lines also showed increased plant tolerance to salt and drought stresses. Further analysis showed that MdIAA29 inhibited the regulation of auxin response factor 4 (ARF4) on Gretchen Hagen 3.9 (GH3.9) gene and 9-cis-epoxycarotenoid dioxygenase 3 (NCED3) gene in apple and changed the contents of auxin and abscisic acid in different tissues, thus achieving a balance between plant height and stress tolerance. In addition, we also found that MdIAA7 enhanced the inhibitory effect of MdIAA29 on MdARF4. In brief, the MdIAA29-MdARF4 complex significantly impacts the height of apple plants and their ability to respond to salt and drought stress.

CsWRKY29, a key transcription factor in tea plant for freezing tolerance, ABA sensitivity, and sugar metabolism

Tea plants (Camellia sinensis L.) are prone to spring frosts, leading to substantial economic damage. WRKY transcription factors are key in plant abiotic stress responses, yet the role of CsWRKY29 in freezing tolerance is unclear. In this study, quantitative real-time PCR (qRT-PCR) and transient green fluorescent protein assay revealed that CsWRKY29 localizes to the nucleus and its expression is induced by cold and abscisic acid (ABA). CsWRKY29 overexpression in Arabidopsis enhanced freezing tolerance, reduced electrolyte leakage, increased soluble sugars, and boosted superoxide dismutase activity, with upregulated COR genes. These lines also showed heightened ABA and glucose sensitivity. Cold treatment of CsWRKY29-overexpressing lines upregulated AtABI5, AtHXK1, and AtSUS4 compared to wild type, and yeast one-hybrid assays confirmed CsWRKY29 binding to the W-box in the CsABI5 promoter. Furthermore, the application of virus-induced gene silencing (VIGS) technology to reduce CsWRKY29 expression in tea plants revealed a significant decrease in the transcript levels of CsCBFs, CsABI5, CsHXK1, and CsSUS4 in the silenced plants. In summary, our findings indicate that CsWRKY29 may serve as a critical transcription factor that contributes to freezing tolerance, ABA responsiveness, and sugar metabolism within tea plants.

Related type 2C protein phosphatases Pic3 and Pic12 negatively regulate immunity in tomato to Pseudomonas syringae

Type 2C protein phosphatases (PP2Cs) constitute a large family in most plant species, but relatively few of them have been implicated in immunity. To identify and characterize PP2C phosphatases that affect tomato (Solanum lycopersicum) immunity, we generated loss-of-function mutations in 11 PP2C-encoding genes whose expression is altered in response to immune elicitors or pathogens. We report that 2 closely related PP2C phosphatases, PP2C immunity-associated candidate 3 (Pic3) and Pic12, are involved in regulating resistance to the bacterial pathogen Pseudomonas syringae pv. tomato (Pst). Loss-of-function mutations in Pic3 led to enhanced resistance to Pst in older but not younger leaves, whereas such mutations in Pic12 resulted in enhanced resistance in both older and younger leaves. Overexpression of Pic3 and Pic12 proteins in leaves of Nicotiana benthamiana inhibited resistance to Pst, and this effect was dependent on Pic3/12 phosphatase activity and an N-terminal palmitoylation motif associated with localization to the cell periphery. Pic3, but not Pic12, had a slight negative effect on flagellin-associated reactive oxygen species generation, although their involvement in the response to Pst appeared independent of flagellin. RNA-sequencing analysis of Rio Grande (RG)-PtoR wild-type plants and 2 independent RG-pic3 mutants revealed that the enhanced disease resistance in RG-pic3 older leaves is associated with increased transcript abundance of multiple defense-related genes. RG-pic3/RG-pic12 double-mutant plants exhibited stronger disease resistance than RG-pic3 or RG-pic12 single mutants. Together, our results reveal that Pic3 and Pic12 negatively regulate tomato immunity in an additive manner through flagellin-independent pathways.

Recent Advances in Studying the Regulation of Fruit Ripening in Tomato Using Genetic Engineering Approaches

Tomato (Solanum lycopersicum L.) is one of the most commercially essential vegetable crops cultivated worldwide. In addition to the nutritional value, tomato is an excellent model for studying climacteric fruits' ripening processes. Despite this, the available natural pool of genes that allows expanding phenotypic diversity is limited, and the difficulties of crossing using classical selection methods when stacking traits increase proportionally with each additional feature. Modern methods of the genetic engineering of tomatoes have extensive potential applications, such as enhancing the expression of existing gene(s), integrating artificial and heterologous gene(s), pointing changes in target gene sequences while keeping allelic combinations characteristic of successful commercial varieties, and many others. However, it is necessary to understand the fundamental principles of the gene molecular regulation involved in tomato fruit ripening for its successful use in creating new varieties. Although the candidate genes mediate ripening have been identified, a complete picture of their relationship has yet to be formed. This review summarizes the latest (2017-2023) achievements related to studying the ripening processes of tomato fruits. This work attempts to systematize the results of various research articles and display the interaction pattern of genes regulating the process of tomato fruit ripening.