Plant Science Research Weekly: June 27, 2025

Special Science Issue: Plants and Heat

The June 12 issue of Science has a focus on plants and heat that includes several excellent review and research articles. In a very interesting review, Singh Yadav et al. discuss the complex and fascinating question of how plants sense temperature, emphasizing both the biophysical nature of temperature perception and the dispersed nature of it in plants. Sam Yeaman wrote a very accessible Perspective on how studying heat adaptations in wild plants can help develop heat-tolerant crops. Laine and Leino address how heat affects plant-microbiome interactions in complex ways. Two additional are reviews are by Bernacchi et al. on strategies to “safeguard photosynthesis” and Evans et al., who look at scale in plant responses “from molecules to biosphere”. This is a timely collection of thought-provoking articles that point to critical research areas needed for food security. (Summary by Mary Williams @PlantTeaching.bsky.social) Science https://www.science.org/doi/full/10.1126/science.adz0700

Theme issue: Crops under stress

They May 29 issue of Phil. Trans. Roy. Soc. B. similarly addresses the pressing questions of how crop plants will continue to feed the world in spite of the rapidly changing climate. This issue covers some of the same topics as the Science special issue on heat stress but goes beyond heat to cover drought stress, salinity stress, and flooding. There are too many outstanding review articles to mention them all here, but I’ll draw your attention to a few. Steve Long wrote an excellent review on “Needs and opportunities to future-proof crops and the use of crop systems to mitigate atmospheric change,” in which he points to clearly effective strategies to improve crop performance that are thwarted by insufficient public funding in crop breeding and the need for private funding to produce a quick return-on-investment, strikingly illustrated by the differences in yield growth in US grown maize versus US grown sorghum or Nigerian-grown cassava (this is a must-read article). Ainsworth et al. address the perennial question of whether crops and CO₂ are friends or foes, looking closely at how increased atmospheric CO₂ can both increase yields and decrease nutritional quality. Other reviews cover growth-promoting microbes, machine learning, stomatal function and more. It is an excellent collection of forward-looking articles. (Summary by Mary Willams @PlantTeaching.bsky.social) Phil. Trans. Roy. Soc. B. https://royalsocietypublishing.org/toc/rstb/2025/380/1927

Review. Going beyond the model: When different plants have different plans

In a recent review, Nieves-Cordones and Rubio highlight the species-specific strategies used by Arabidopsis and crop plants to regulate potassium (K⁺) and sodium (Na⁺) transport, which challenges the universality of Arabidopsis thaliana research. In Arabidopsis, K⁺ uptake is largely mediated by AKT1-type voltage-gated channels, whereas crops like rice and tomato rely more heavily on HAK5-type K⁺/H⁺ symporters, particularly under low external K⁺ conditions. These differences are likely shaped by variations in membrane potential, metabolic cost, and evolutionary context. Notably, crops possess clade IV HAK transporters—absent in Arabidopsis—that facilitate Na⁺ retrieval from the xylem and contribute to salt tolerance, especially in vascular tissues. In reproductive organs, HAK5-like transporters are essential for pollen viability and fertility in tomato and rice, with mutations leading to reduced seed set or even parthenocarpy, highlighting their agronomic relevance. The study also uncovers species-specific rewiring of Ca²⁺-dependent CBL-CIPK signaling networks, with tomato and rice exhibiting regulatory controls that are either absent or divergent in Arabidopsis. Taken together, these findings underscore the limitations of extrapolating from Arabidopsis alone and advocate for broader comparative studies to uncover the diversity of ion transport solutions evolved across plant lineages. (Summary by Stephanie Temnyk @STemnyk) Trends in Plant Science 10.1016/j.tplants.2025.05.007

Multimerization of IAA3 via ROS suppresses lateral root formation in air gaps

Root growth and branching is strongly tuned to environmental conditions including soil compaction, nutrient availability, and the presence of water, with auxin having a major role in regulating root architecture. Here, Roy et al. have demonstrated how auxin contributes to a suppression of root branching in a dry region, which is known as xerobranching (from the Greek word xēros, meaning dry). The authors showed that reactive oxygen species (ROS) accumulate in air-gap tissues, and mutants in reactive oxygen production (rboh mutants) fail to suppress branching in air gaps and show lower levels of ROS in the air-gap tissues. They hypothesized that the transcriptional repressor IAA3, a key regulator of root branching, was responsible for the xerobranching, and they found that in the presence of ROS, IAA3 forms multimers, leading to the suppression auxin-responsive genes. Thus, the air-gap is signaled by ROS accumulation in root nuclei, which suppresses the formation of lateral roots in these dry regions. (Summary by Mary Williams @PlantTeaching.bsky.social) Science 10.1126/science.adu1470

Identity is Everything : MYB68 regulates endodermal differentiation and suberin patterning

Root cells are organized into concentric layers that facilitate the movement of water and nutrients. Among these, the endodermis overlays the root vasculature, allowing it to play a major role in selective uptake. To perform this function, endodermal cells undergo two distinct stages of differentiation. The first stage involves the formation of the Casparian strip barrier that prevents extracellular diffusion, while the second leads to the deposition of suberin, a hydrophobic polymer that seals off the vasculature. However, some endodermal cells are not suberized, forming patchy zones in the barrier known as passage cells, which are hypothesized to provide low-resistance routes for selective uptake. In Arabidopsis, the central vasculature is arranged in opposing poles of xylem and phloem, and to function effectively, endodermal cells align with one of three positional identities: xylem pole-associated (XPE), phloem pole-associated (PPE), or non-pole-associated (NPE). In this study, Kraska et al. identified a MYB-class transcription factor, MYB68, as a regulator of suberin patterning in XPE and NPE cell files. MYB68 knockout lines showed reduced suberization frequency in both XPE and NPE files, alongside expanded patchy zones in XPE files. Despite these spatial disruptions, the onset of suberization and the overall patterning rate remained comparable to wild type, suggesting that MYB68 functions within an age-dependent regulatory network rather than initiating suberization. To further investigate MYB68’s role in suberin patterning, the authors used a transcriptional marker for a gene typically expressed in passage cells and observed a significant increase in expression in the mutants, indicating that MYB68 represses passage cell identity. This work lays the foundation for decoding the genetic network that patterns endodermal cell identity and suberization. (Summary by Irene I. Ikiriko @ireneikiriko) Cell Reports 10.1016/j.celrep.2025.115794

The shape of adaptation: Evolution of venation patterns in plants

Leaf venation patterns display remarkable diversity across both living and fossil plant lineages, yet key questions remain about when and how these architectural differences emerged and what functional roles they serve. In their recent review, Mantos et al. explored the evolutionary history of venation traits and vein sizes across vascular plants using a dataset of 1,000 species, including both extant and extinct taxa. This comprehensive approach enabled them to reconstruct nearly 400 million years of venation network evolution. Their analysis focused on four venation traits across small, medium, and large vein size classes. Results revealed an evolutionary shift from simpler networks, characterized by fewer veins and more, corrugated loops, to more complex structures with more veins and smoother, less frequent loops. To assess how venation diversity changed over time, the authors performed a disparity-through-time (DTT) analysis. They identified two peaks in architectural diversification: one in the Paleozoic, followed by a decline during the Cretaceous, and a second, ongoing wave in the Cenozoic, largely driven by modern angiosperms. Environmental drivers were also examined. While no strong correlation was found between venation traits and climate variables such as CO₂ or temperature, a positive relationship emerged between insect diversification and specific traits in small and medium veins. These findings raise important questions about the multiple selective pressures underlying vein evolution, including the potential roles of hydraulic efficiency, mechanical support, and herbivory resistance. Increased vein density and smoother loops may have improved water transport, while also reinforcing leaf structure and protection from insect damage. Overall, this study offers a rich and nuanced view of leaf venation evolution, highlighting its complexity, diversity, and ecological significance. (Summary by Elisa De Meo, www.linkedin.com/in/elisa-de-meo-25415a20b) Nature Plants, 10.1038/s41477-025-02011-y.

PIN auxin transporters facilitate polar transport of synthetic phenoxyacetic acid herbicides

Synthetic herbicides are widely used in agriculture to control weeds, often by targeting the physiological pathways regulated by auxins, plant hormones that induce root growth and development. PIN-FORMED (PIN) auxin transporters facilitate the polar transport of natural auxins such as indole-3-acetic acid (IAA) out of the cell. To determine whether phenoxyacetic acid herbicides (synthetic auxins) are similarly transported by PIN transporters, Schulz and coworkers evaluated the transport kinetics of synthetic auxins via PIN8. The authors found that 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chlorophenoxyacetic acid (4-CPA) were transported in the presence of PIN8, with transport kinetics resembling IAA. Notably, the binding affinity varied depending on the chemical structure of the substrates. Using Cryo-EM, the authors resolved the structure of PIN8 and explored the molecular interactions that direct the transport dynamics. Five conformations occur during the transport event, which reflect a multistep process that involves substrate recognition, binding, and release. Structure-guided mutagenesis further identified key residues determining substrate specificity. The configuration of the binding site directs the substrate movement to the vestibule of the transporter and out of the cell. This study lays the groundwork for the identification and design of novel herbicides, as well as for the manipulation of plant physiology to confer herbicide resistance through synthetic biochemistry and protein engineering. (Summary by Jerry González Cantoral @phytojerry.bsky.social) Nature Plants. 10.1038/s41477-025-01984-0

Artificial condensates can boost metabolic engineering

Nicotiana benthamiana is widely used to reconstruct complex, multi-step metabolic pathways for research or industrial purposes. This is enabled by rapid and high-level protein expression after agroinfiltration. Within cells, as well as membrane-bound organelles, nonmembrane-bound biomolecular condensates can spontaneously form with high concentrations of specific proteins and biochemicals. Battle et al. used the disordered RGG domain from a C. elegans protein known to phase separate, and engineered a scaffold to create synthetic condensates in N. benthamiana. One half of a cognate pair of synthetic coiled-coil peptides (SYNZIP1) is bound to these RGG domains, and attaching the other to a protein of your choice recruits it to the condensate. These condensates were round, liquid-like, and showed molecular exchange between condensates, key characteristics of phase-separating systems. While in this condensate, proteins were shown to have increased stability, and their activity may also be boosted due to proximity to their substrates and protection from degradation. The usefulness of this system was demonstrated using the citramalate biosynthesis pathway, used in plastic manufacturing. By targeting citramalate synthase to condensates, the level of citramalate produced more than doubled. These advances could improve the use of N. benthamiana as factories for the production of economically and industrially important chemical compounds.  (Summary by Ciara O’Brien @ciara-obrien.bsky.social) Plant Biotechnol. J. 10.1111/pbi.70082

Elucidation and recreation of the biosynthetic pathway for taxol

Paclitaxel (sold as Taxol) is taxane diterpene natural product of yew trees (Taxus spp.)  and a potent stabilizer of microtubules that is effective in treatment of cancers. However, it has proven difficult to elucidate its biosynthetic pathway, and commercial production still relies on extracting an intermediate, baccatin III, from yew tissues. In an elegant new work by McClune and Liu et al., the authors used a novel approach to identify genes involved in paclitaxel synthesis. By doing so, they discovered several new genes in the pathway, enabling them to synthesize baccatin III heterologously in Nicotiana benthamiana leaves. Part of the challenge lies in the fact that yews produce hundreds of closely related taxanes, and correspondingly hundreds of candidate biosynthetic genes. The authors developed a new pipeline to search for these elusive paclitaxel genes which they termed multiplexed perturbation × single nuclei (mpXsn). One of the key advantages of this process is that they were able to simultaneously profile cells from many tissues, developmental stages, and responding to various potential inducers of paclitaxel synthesis. Interestingly, several of the genes that they identified had not previously been considered as candidates. Not only does this work provide an exciting new process for Taxol synthesis that does not require harvesting yew tissue, but the mpXsn technology does not require any genetic tools so is generalizable to diverse, non-model species. (Summary by Mary Williams @PlantTeaching.bsky.social) Nature 10.1038/s41586-025-09090-z

A translational brake on ABA biosynthesis shapes germination timing and sprouting resistance

Seed germination is a critical developmental switch that depends not only on stored mRNA but also on the selective translation of these transcripts. In this study, Wang et al. explored how translational control of some genes can fine-tune the timing of germination.  Using translation inhibitors and ribosome-defective mutants in Arabidopsis thaliana, the authors showed that active translation is essential for timely germination. Polysome profiling and RNA-seq analyses uncover widespread remodeling of the translational landscape during early germination. One key finding is that ABA2, a gene encoding a central enzyme in the ABA biosynthesis pathway, contains an upstream open reading frame (uORF) in its 5′ untranslated region that suppresses translation of the main coding sequence. Disrupting the ABA2 uORF increases ABA2 protein levels and delays germination. The effect is reversed in aba2 mutants or upon treatment with an ABA biosynthesis inhibitor, confirming a functional link. The study further shows that similar uORF-mediated control exists in rice, where mutations in the OsABA2 uORF reduce preharvest sprouting (PHS). Natural variation in this uORF among rice cultivars correlates with differences in PHS, suggesting it was shaped by domestication and selection. This work identifies a conserved translational control mechanism governing ABA accumulation and germination behavior and introduces uORF variants as potential tools for improving dormancy and sprouting resistance in crops.  (Summary by Muhammad Aamir Khan @MAKNature1998)  PNAS  10.1073/pnas.250215512

A phosphorylation switch balances growth and stress response in cotton

Salt stress can severely affect cotton (Gossypium hirsutum) productivity, especially during early growth. Cao et al. identified a molecular switch in cotton that fine-tunes responses to salt stress and the hormone abscisic acid (ABA), based on the reversible phosphorylation of the ABA signaling phosphatase GhABI1. The authors found that GhRAF36, a Raf-like protein kinase, phosphorylates GhABI1 at two cotton-specific residues, suppressing its activity and activating ABA signaling. This promotes salt-stress responses. In contrast, GhTOPP4aD, a Type One Protein Phosphatase, counteracts this by dephosphorylating both GhRAF36 and GhABI1, thereby repressing ABA signaling. Under salt stress, GhTOPP4aD protein levels decrease, allowing GhRAF36 to dominate and drive ABA activation. Functional experiments, including gene silencing and overexpression in cotton, show that GhTOPP4aD negatively regulates salt tolerance and ABA sensitivity, while GhRAF36 enhances them. Epistasis analyses further confirm that GhRAF36 and GhABI1 operate downstream of GhTOPP4aD in this pathway. This GhTOPP4aD–GhRAF36–GhABI1 module serves as a reversible phosphorylation circuit that integrates stress signals with hormone responses. It provides new insights into how cotton balances growth and stress resilience and offers targets for improving stress tolerance in crop breeding. (Summary by Muhammad Aamir Khan @MAKNature1998)  Plant Biotechnol. J. 10.1111/pbi.70166