A rapid and appropriate genetic and metabolic acclimation, which is crucial for plants’ survival in a changing environment, is maintained due to the coordinated action of plant hormones and cellular degradation mechanisms influencing proteostasis. The plant hormone abscisic acid (ABA) rapidly accumulates in plants in response to environmental stress and plays a pivotal role in the reaction to various stimuli. Increasing evidence demonstrates a significant role of autophagy in controlling ABA signaling. This field has been extensively investigated and new discoveries are constantly being provided. We present updated information on the components of the ABA signaling pathway, particularly on transcription factors modified by different E3 ligases. Then, we focus on the role of selective autophagy in ABA pathway control and review novel evidence on the involvement of autophagy in different parts of the ABA signaling pathway that are important for crosstalk with other hormones, particularly cytokinins and brassinosteroids.

Broomrape (Orobanche cumana), root parasitic weed, negatively affects sunflower, thereby causing severe yield losses and required controls on O. cumana infestation. Brassinosteroids (BRs) plays key roles in plant growth and provides resilience to weed infection. This designed study evaluated the mechanisms by which BRs ameliorates O. cumana infection in sunflower (Helianthus annuus). The pretreatment of sunflower seeds with various concentrations of BRs (1, 10, and 100 nM) were applied with and without O. cumana infestation. Under O. cumana infection, a significant reduction in plant height (38.61%), fresh/dry biomass, photosynthesis and regulation in plant defense (POX, GST), BRs signaling (BAK1, BSK1 to BSK4) and synthesis (BRI1, BR6OX2) associated genes. Moreover, O. cumana elevated the levels of MDA, OH‒, H2O2 and O2•‒ in leaves/roots by 77%/112%, 62%/104%, 57%/98% and 55%/89.4% and caused ultrastructural damages in leaves/roots, suggesting the severe oxidative or cellular damages in sunflower. In response, plants activate activities of SOD and POD enzymes as well as reduced or oxidized glutathione, but unable to stimulate APX and CAT activities. Addition of BRs, especially at 10 nM notably lowered the production of oxidative stress, activated the enzymatic and non-enzymatic antioxidants. The downregulation in the reported genes by BRs attributed to the increased resilience of sunflower (via susceptible reaction). In nutshell, the pretreatment of BRs enhanced the sunflower resistance to O. cumana infection by improving the planta growth and biomass, photosynthesis, activating the antioxidant defense system, lowering the oxidative stress, cellular damages and modulating the expression of BR synthesis and signaling genes.

Huanglongbing (HLB), or citrus greening, is a devastating disease impacting citrus trees worldwide, with severe effects particularly noted in Florida. Current strategies to combat HLB have focused on aggressive replanting despite the high susceptibility of young trees to infection. In this context, it is critical to explore agronomic practices that can enhance the health and resistance of young citrus trees to HLB. Here, we demonstrate that treatment with homobrassinolide (HBr), a type of brassinosteroid, on newly planted citrus trees can delay HLB infection and improve tree health amidst the high psyllid pressure conditions endemic to Florida. Our study reveals a significant reduction in HLB infection rates in HBr-treated trees compared to control trees, with only 25% of treated trees testing positive for HLB by six months, in contrast to 100% infection in untreated trees. This delay in infection may be attributed to HBr inducing an immune response and negatively impacting psyllid performance, as subsequently demonstrated in a greenhouse experiment. Our findings suggest that HBr applications could serve as a viable strategy to enhance the resilience of citrus production against HLB, underscoring the need for further investigation into their mechanisms of action and potential role in a comprehensive pest and disease management strategy.