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1. Periplasmic stress contributes to a trade-off between protein secretion and cell growth in  Escherichia coli Nissle 1917

   https://doi.org/10.1093/synbio/ysad013  

   Emani, Sivaram Subaya; Kan, Anton; Storms, Timothy; Bonanno, Shanna; Law, Jade; Ray, Sanhita; Joshi, Neel S. (July 2023, Synthetic Biology)

   Abstract Maximizing protein secretion is an important target in the design of engineered living systems. In this paper, we characterize a trade-off between cell growth and per-cell protein secretion in the curli biofilm secretion system of Escherichia coli Nissle 1917. Initial characterization using 24-h continuous growth and protein production monitoring confirms decreased growth rates at high induction, leading to a local maximum in total protein production at intermediate induction. Propidium iodide (PI) staining at the endpoint indicates that cellular death is a dominant cause of growth reduction. Assaying variants with combinatorial constructs of inner and outer membrane secretion tags, we find that diminished growth at high production is specific to secretory variants associated with periplasmic stress mediated by outer membrane secretion and periplasmic accumulation of protein containing the outer membrane transport tag. RNA sequencing experiments indicate upregulation of known periplasmic stress response genes in the highly secreting variant, further implicating periplasmic stress in the growth–secretion trade-off. Overall, these results motivate additional strategies for optimizing total protein production and longevity of secretory engineered living systems Graphical Abstract 

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2. Brachypodium distachyon MAP20 functions in metaxylem pit development and contributes to drought recovery

   https://doi.org/10.1111/nph.16383  

   Smertenko, Tetyana; Turner, Glenn; Fahy, Deirdre; Brew‐Appiah, Rhoda A. T.; Alfaro‐Aco, Raymundo; de Almeida Engler, Janice; Sanguinet, Karen A.; Smertenko, Andrei (February 2020, New Phytologist)

   Summary Pits are regions in the cell walls of plant tracheary elements that lack secondary walls. Each pit consists of a space within the secondary wall called a pit chamber, and a modified primary wall called the pit membrane. The pit membrane facilitates transport of solutions between vessel cells and restricts embolisms during drought. Here we analyzed the role of an angiosperm‐specific TPX2‐like microtubule protein MAP20 in pit formation usingBrachypodium distachyonas a model system.Live cell imaging was used to analyze the interaction of MAP20 with microtubules and the impact of MAP20 on microtubule dynamics. MAP20‐specific antibody was used to study expression and localization of MAP20 in different cell types during vascular bundle development. We used an artificial microRNAs (amiRNA) knockdown approach to determine the function ofMAP20.MAP20 is expressed during the late stages of vascular bundle development and localizes around forming pits and under secondary cell wall thickenings in metaxylem cells. MAP20 suppresses microtubule depolymerization; however, unlike the animal TPX2 counterpart, MAP20 does not cooperate with the γ‐tubulin ring complex in microtubule nucleation. Knockdown ofMAP20causes bigger pits, thinner pit membranes, perturbed vasculature development, lower reproductive potential and higher drought susceptibility.We conclude thatMAP20may contribute to drought adaptation by modulating pit size and pit membrane thickness in metaxylem. 

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3. Stachydrine Catabolism Contributes to an Optimal Root Nodule Symbiosis Between Sinorhizobium meliloti and Medicago sativa

   https://doi.org/10.1094/MPMI-02-25-0021-SC  

   Levin, Garrett J; Kearsley, Jason_V S; Finan, Turlough M; Geddes, Barney A (August 2025, Molecular Plant-Microbe Interactions®)

   Sinorhizobium meliloti forms a robust N₂-fixing root-nodule symbiosis with Medicago sativa. We are interested in identifying the minimal symbiotic genome of the model strain S. meliloti Rm1021. This gene set refers to the minimal genetic determinants required to form a robust N₂-fixing symbiosis. Many symbiotic genes are located on the 1,354 kb pSymA megaplasmid of S. meliloti Rm1021. We recently constructed a minimalized pSymA, minSymA2.1, that lacked over 90% of the pSymA genes. Relative to the wild-type, minSymA2.1 showed a reduction in M. sativa shoot biomass production and nodule size with an increase in total nodule number. Here we show that the addition of either the stachydrine (stc) or trigonelline (trc) catabolism genes from pSymA to minSymA2.1 restores nodule size and total nodule number to levels indistinguishable from the wild-type but does not restore reduced shoot biomass production. In the context of the complete Rm1021 genome, removing the stc genes reduced nodule size and increased total nodule number while removal of the trc genes alone had no apparent effect. Together, these observations implicate stachydrine catabolism as an important determinant of root nodule symbiosis between S. meliloti and M. sativa while trigonelline catabolism seems to contribute in a more conditional manner, in the context of the minimized genome. These findings highlight the minimal symbiotic genome as a tool for investigating the impact individual genetic determinants have in conferring an optimal symbiosis. Factors whose impact, in the context of a complete genome, may be hidden or dampened due to redundancies. 

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4. The FATTY ACID DESATURASE2 Family in Tomato Contributes to Primary Metabolism and Stress Responses

   https://doi.org/10.1104/pp.19.00487  

   Lee, Min Woo; Padilla, Carmen S.; Gupta, Chirag; Galla, Aravind; Pereira, Andy; Li, Jiamei; Goggin, Fiona L. (January 2020, Plant Physiology)
5. Response of Hydroponic Tomato Yield and Yield-correlated Morphological Characteristics to Constant or Growth Stage-based Nutrient Management Strategies

   https://doi.org/10.21273/HORTSCI18044-24  

   Dunn, Ronnie J; Nattrass, Michael (October 2024, HortScience)

   In the United States, the annual revenue attributable to tomato production is $1 billion. However, tomato production can cause negative environmental impacts, such as water pollution, often in the form of eutrophication-causing nutrient pollution. Hydroponic production can decrease excess nutrient leaching; however, optimization of nutrient management and cultivar choices could further decrease excess nutrient discharges. The objectives of this study were as follows: to evaluate and compare the responses of tomato growth characteristics, yield, and yield components to two nutrient management regimes (varying nutrient solution concentrations by growth stage and the use of a constant nutrient solution concentration from transplant to termination), and to analyze the effects of growth habits among six cultivars (Big Beef, Cherokee Purple, Heatmaster, Legend, Mountain Fresh Plus, and Tropic) on tomato yield and yield-correlated morphological characteristics. The nutrient management strategies were applied to tomato plants, and data regarding yield and related morphological characteristics were obtained. Data were analyzed using SAS PROC GLM. An analysis revealed no significant difference in the total fruit weight/plant between nutrient management regimes (P= 0.05); however, the mean fruit weight (164.26 g) and diameter (71.70 mm) were significantly greater (P< 0.0001) for plants that received the constant concentration nutrient regime. Indeterminate plants had a significantly greater (P< 0.0001) mean fruit weight (192.76 g) and mean fruit diameter (76.42 mm). Among cultivars, Big Beef had a significantly greater (P< 0.05) total fruit weight/plant (9.25 kg). Applying a constant nutrient concentration to indeterminate cultivars, particularly Big Beef and Cherokee Purple, improved the factors analyzed and could decrease negative environmental impacts while increasing profits of the producers. 

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