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1. From growth to stress: RAF-like kinases as integrators of hormonal signals in plants

   https://doi.org/10.1093/jxb/eraf086  

   Park, Hye Lin; Yoon, Gyeong Mee (March 2025, Journal of Experimental Botany)

   McSteen, Paula (Ed.)

   Abstract RAF-like kinases, members of the mitogen-activated protein kinase kinase kinase (MAPKKK) family, are central integrators of external and internal signals in plant stress responses and growth regulation. These kinases mediate signaling through multiple hormone pathways, including abscisic acid-dependent and -independent pathways, ethylene signaling, and rapid auxin responses. Unlike typical MAPKKKs that function through kinase cascades, RAF-like kinases primarily employ direct phosphorylation of downstream targets and dynamic subcellular localization to mediate specific physiological responses. Here, we review the emerging roles of RAF-like kinases in Arabidopsis thaliana, highlighting their integrative functions in hormone signaling, stress responses, and growth control. The complex interplay between different RAF-like kinase subgroups and their diverse cellular targets underscores the intricate regulatory mechanisms plants have evolved to coordinate environmental responses with development. 

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2. Cross-species predictive modeling reveals conserved drought responses between maize and sorghum

   https://doi.org/10.1073/pnas.2216894120  

   Pardo, Jeremy; Wai, Ching Man; Harman, Maxwell; Nguyen, Annie; Kremling, Karl A; Romay, Maria Cinta; Lepak, Nicholas; Bauerle, Taryn L; Buckler, Edward S; Thompson, Addie M; et al (March 2023, Proceedings of the National Academy of Sciences)

   Drought tolerance is a highly complex trait controlled by numerous interconnected pathways with substantial variation within and across plant species. This complexity makes it difficult to distill individual genetic loci underlying tolerance, and to identify core or conserved drought-responsive pathways. Here, we collected drought physiology and gene expression datasets across diverse genotypes of the C4 cereals sorghum and maize and searched for signatures defining water-deficit responses. Differential gene expression identified few overlapping drought-associated genes across sorghum genotypes, but using a predictive modeling approach, we found a shared core drought response across development, genotype, and stress severity. Our model had similar robustness when applied to datasets in maize, reflecting a conserved drought response between sorghum and maize. The top predictors are enriched in functions associated with various abiotic stress-responsive pathways as well as core cellular functions. These conserved drought response genes were less likely to contain deleterious mutations than other gene sets, suggesting that core drought-responsive genes are under evolutionary and functional constraints. Our findings support a broad evolutionary conservation of drought responses in C4 grasses regardless of innate stress tolerance, which could have important implications for developing climate resilient cereals. 

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3. Adaptive Remodeling of the Proteome in Pistachio Roots Under Salt Stress: Implications for Food and Energy Security in Arid Regions

   https://doi.org/10.1002/fes3.70151  

   Akbari, Mohammad; Singh, Rakesh K; Andriūnaitė, Elena; Reddy, Umesh; Farajpour, Mostafa; Simmons, Sanaa; Vishnudasan, Dalia; Charles, Sona; Suravajhala, Prashanth; Mahna, Nasser; et al (November 2025, Food and Energy Security)

   ABSTRACT Pistachio thrives in semi‐arid and arid environments and is highly adaptable to various abiotic stresses. However, soil salinization significantly threatens productivity, leading to considerable osmotic and ionic stress for these plants. Roots are the primary sites for stress perception and response; however, they remain understudied in woody crops, such asPistachio. This study examines the alterations in root protein expression and metabolic pathways in response to sodium chloride‐induced salt stress through biochemical and proteomic analyses. One‐year‐old pistachio rootstocks were treated with four different saline water regimes over a 100‐day period, and the total proteins were isolated from these samples. Over 1600 protein identifiers were detected, with comparative analysis revealing 245 proteins that were more abundant and 190 that were less abundant across three stress levels. Key pathways associated with stress tolerance, such as protein modification, folding, and heat shock protein (HSP) protection, were upregulated. An increase in secondary metabolites played a crucial role in detoxification. As salt stress intensified, the abundance of trafficking proteins increased, enhancing transporter activities. Active signaling pathways were observed at lower stress levels, while structural proteins became more critical at higher stress levels for maintaining cell membrane integrity. This cultivar exhibited enhanced kinase activities that regulate lipid and carbohydrate metabolism, thereby aiding in ion homeostasis and maintaining redox balance. The protein interaction network, mapped to orthologous proteins inArabidopsis thaliana, revealed clusters associated with cytosolic, carbohydrate, and amino acid metabolism contributing to salinity stress tolerance. The validation of proteomic data was performed by assessing corresponding changes in transcript levels. The study expands upon previous work by providing a comprehensive proteomic map of UCB‐1 pistachio rootstock across multiple salinity levels. The findings have practical implications for developing more resilient cultivars, supporting sustainable pistachio production in regions prone to salinity. 

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4. Overexpression of stress granule protein TZF1 enhances salt stress tolerance by targeting ACA11 mRNA for degradation in Arabidopsis

   https://doi.org/10.3389/fpls.2024.1375478  

   He, Siou-Luan; Li, Bin; Zahurancik, Walter J; Arthur, Henry C; Sidharthan, Vaishnavi; Gopalan, Venkat; Wang, Lei; Jang, Jyan-Chyun (May 2024, Frontiers in Plant Science)

   Tandem CCCH zinc finger (TZF) proteins play diverse roles in plant growth and stress response. Although as many as 11 TZF proteins have been identified inArabidopsis, little is known about the mechanism by which TZF proteins select and regulate the target mRNAs. Here, we report thatArabidopsisTZF1 is a bona-fide stress granule protein. Ectopic expression ofTZF1(TZF1 OE), but not an mRNA binding-defective mutant (TZF1^H186YOE), enhances salt stress tolerance inArabidopsis. RNA-seq analyses of NaCl-treated plants revealed that the down-regulated genes inTZF1 OEplants are enriched for functions in salt and oxidative stress responses. Because many of these down-regulated mRNAs contain AU- and/or U-rich elements (AREs and/or UREs) in their 3’-UTRs, we hypothesized that TZF1—ARE/URE interaction might contribute to the observed gene expression changes. Results from RNA immunoprecipitation-quantitative PCR analysis, gel-shift, and mRNA half-life assays indicate that TZF1 binds and triggers degradation of theautoinhibited Ca²⁺-ATPase 11(ACA11) mRNA, which encodes a tonoplast-localized calcium pump that extrudes calcium and dampens signal transduction pathways necessary for salt stress tolerance. Furthermore, this salt stress-tolerance phenotype was recapitulated inaca11null mutants. Collectively, our findings demonstrate that TZF1 binds and initiates degradation of specific mRNAs to enhance salt stress tolerance. 

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5. Leaf isoprene emission as a trait that mediates the growth-defense tradeoff in the face of climate stress

   https://doi.org/10.1007/s00442-020-04813-7  

   Monson, Russell K.; Weraduwage, Sarathi M.; Rosenkranz, Maaria; Schnitzler, Jörg-Peter; Sharkey, Thomas D. (November 2020, Oecologia)

   null (Ed.)

   Plant isoprene emissions are known to contribute to abiotic stress tolerance, especially during episodes of high temperature and drought, and during cellular oxidative stress. Recent studies have shown that genetic transformations to add or remove isoprene emissions cause a cascade of cellular modifications that include known signaling pathways, and interact to remodel adaptive growth-defense tradeoffs. The most compelling evidence for isoprene signaling is found in the shikimate and phenylpropanoid pathways, which produce salicylic acid, alkaloids, tannins, anthocyanins, flavonols and other flavonoids; all of which have roles in stress tolerance and plant defense. Isoprene also influences key gene expression patterns in the terpenoid biosynthetic pathways, and the jasmonic acid, gibberellic acid and cytokinin signaling networks that have important roles in controlling inducible defense responses and influencing plant growth and development, particularly following defoliation. In this synthesis paper, using past studies of transgenic poplar, tobacco and Arabidopsis, we present the evidence for isoprene acting as a metabolite that coordinates aspects of cellular signaling, resulting in enhanced chemical defense during periods of climate stress, while minimizing costs to growth. This perspective represents a major shift in our thinking away from direct effects of isoprene, for example, by changing membrane properties or quenching ROS, to indirect effects, through changes in gene expression and protein abundances. Recognition of isoprene’s role in the growth-defense tradeoff provides new perspectives on evolution of the trait, its contribution to plant adaptation and resilience, and the ecological niches in which it is most effective. 

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