Epidermal bladder cells as a herbivore defense mechanism

Functional identification of two Glycerol-3-phosphate Acyltransferase5 homologs from Chenopodium quinoa

Glycerol-3-phosphate acyltransferase5 (GPAT5) is the key enzyme in suberin biosynthesis in Arabidopsis, tomato and Sarracenia purpurea. However, little is known about whether GPAT5 function is conserved in halophytes. In this study, we identified two GPAT5 homologs, CqGPAT5a and CqGPAT5b, in Chenopodium quinoa, the typical halophyte. Using RT-qPCR, we found that CqGPAT5a and CqGPAT5b were highly expressed in quinoa roots and rapidly induced by high salt stress. CqGPAT5a and CqGPAT5b were localized to the endoplasmic reticulum and found to have glycerol-3-phosphate acyltransferase activity using yeast complementation assays. Compared with CqGPAT5b, CqGPAT5a showed relatively weaker function and less protein abundance when expressed in yeast, Arabidopsis or Nicotiana benthamiana. Subsequently, we identified a serine (S) to leucine (L) variation in the CqGPAT5a protein sequence (S251L) compared with CqGPAT5b, located in the connecting region between the second and third transmembrane domains. Site-directed mutagenesis together with yeast mutant complementation and transient expression in tobacco demonstrated that this variation significantly affected CqGPAT5a activity and protein abundance. These findings expand our understanding of GPAT5 and provide new evidence that GPAT5 may be functionally conserved in halophytes.

Regulatory effect of pipecolic acid (Pip) on the antioxidant system activity of Mesembryanthemum crystallinum plants exposed to bacterial treatment

The presented study aims to elucidate the regulatory role of Pipecolic acid (Pip) in modulating the antioxidant system activity of Mesembryanthemum crystallinum plants exposed to Pseudomonas syringae infestation. M. crystallinum, known for its semi-halophytic nature, can transition its metabolism from C3 to CAM under salt stress conditions. The research encompasses the antioxidant system of the plants, covering both enzymatic and low molecular weight components. The findings indicate that Pip supplementation confers a beneficial effect on certain elements of the antioxidant system when the plants are subjected to stress induced by bacteria. Notably, during critical periods, particularly in the initial days post-bacterial treatment, M. crystallinum plants supplemented with Pip and exhibiting C3 metabolism display heightened total antioxidant capacity. This enhancement includes increased superoxide dismutase activity and elevated levels of glutathione and proline. However, in plants with salinity-induced CAM, where these parameters are naturally higher, the supplementation of Pip does not yield significant effects. These results validate the hypothesis that the regulatory influence of Pip on defence mechanisms against biotic stress is contingent upon the metabolic state of the plant. Furthermore, this regulatory effect is more pronounced in C3 plants of M. crystallinum than those undergoing CAM metabolism induced by salinity stress.

Understanding the salinity resilience and productivity of halophytes in saline environments

The escalating salinity levels in cultivable soil pose a significant threat to agricultural productivity and, consequently, human sustenance. This problem is being exacerbated by natural processes and human activities, coinciding with a period of rapid population growth. Developing halophytic crops is needed to ensure food security is not impaired and land resources can be used sustainably. Evolution has created many close halophyte relatives of our major glycophytic crops, such as Puccinellia tenuiflora (relative of barley and wheat), Oryza coarctata (relative of rice) and Glycine soja (relative of soybean). There are also some halophytes have been subjected to semi-domestication and are considered as minor crops, such as Chenopodium quinoa. In this paper, we examine the prevailing comprehension of robust salinity resilience in halophytes. We summarize the existing strategies and technologies that equip researchers with the means to enhance the salt tolerance capabilities of primary crops and investigate the genetic makeup of halophytes.

Quinoa: A Promising Crop for Resolving the Bottleneck of Cultivation in Soils Affected by Multiple Environmental Abiotic Stresses

Quinoa (Chenopodium quinoa Willd.) has gained worldwide recognition for its nutritional values, adaptability to diverse environments, and genetic diversity. This review explores the current understanding of quinoa tolerance to environmental stress, focusing on drought, salinity, heat, heavy metals, and UV-B radiation. Although drought and salinity have been extensively studied, other stress factors remain underexplored. The ever-increasing incidence of abiotic stress, exacerbated by unpredictable weather patterns and climate change, underscores the importance of understanding quinoa's responses to these challenges. Global gene banks safeguard quinoa's genetic diversity, supporting breeding efforts to develop stress-tolerant varieties. Recent advances in genomics and molecular tools offer promising opportunities to improve stress tolerance and increase the yield potential of quinoa. Transcriptomic studies have shed light on the responses of quinoa to drought and salinity, yet further studies are needed to elucidate its resilience to other abiotic stresses. Quinoa's ability to thrive on poor soils and limited water resources makes it a sustainable option for land restoration and food security enterprises. In conclusion, quinoa is a versatile and robust crop with the potential to address food security challenges under environmental constraints.

Structure, ultrastructure and cation accumulation in quinoa epidermal bladder cell complex under high saline stress

Quinoa is a facultative halophyte with excellent tolerance to salinity. In this study, the epidermal bladder cell complex (EBCc) of quinoa leaves was studied to determine their cellular characteristics and involvement in salt tolerance. We used light microscopy, confocal RAMAN microscopy, confocal fluorescence microscopy, transmission electron microscopy, and environmental scanning electron microscopy complemented by energy dispersive X-ray analysis. Ionic content was quantified with flame atomic absorption spectroscopy and with flame emission photometry. Results show that: (i) the number of EBCcs remains constant but their density and area vary with leaf age; (ii) stalk cells store lipids and exhibit thick walls, bladder cells present carotenes in small vesicles, oxalate crystals in vacuoles and lignin in their walls and both stalk and bladder cells have cuticles that differ in wax and cutin content; (iii) chloroplasts containing starch can be found on both stalk and bladder cells, and the latter also presents grana; (iv) plasmodesmata are observed between the stalk cell and the bladder cell, and between the epidermal cell and the stalk cell, and ectodesmata-like structures are observed on the bladder cell. Under high salinity conditions, (v) there is a clear tendency to accumulate greater amounts of K+ with respect to Na+ in the bladder cell; (vi) stalk cells accumulate similar amounts of K+ and Na+; (vii) Na+ accumulates mainly in the medullary parenchyma of the stem. These results add knowledge about the structure, content, and role of EBCc under salt stress, and surprisingly present the parenchyma of the stem as the main area of Na+ accumulation.

Plant physiology: The overturning of assumed functional relevance of 'salt' bladders

For decades, the function of epidermal bladder cells in quinoa and iceplant was thought to be physiological because of their function in a related species. Exciting new research carefully demolishes that assumption, suggesting that these structures serve primarily biotic defense roles, setting up a great many interesting, important questions.