Molecular Characterization of LjABCG1, an ATP-Binding Cassette Protein in Lotus japonicus

Biosynthesis and metabolic engineering of isoflavonoids in model plants and crops: a review

Isoflavonoids, the major secondary metabolites within the flavonoid biosynthetic pathway, play important roles in plant defense and exhibit free radical scavenging properties in mammals. Recent advancements in understanding the synthesis, transport, and regulation of isoflavonoids have identified their biosynthetic pathways as promising targets for metabolic engineering, offering potential benefits such as enhanced plant resistance, improved biomass, and restoration of soil fertility. This review provides an overview of recent breakthroughs in isoflavonoid biosynthesis, encompassing key enzymes in the biosynthetic pathway, transporters influencing their subcellular localization, molecular mechanisms regulating the metabolic pathway (including transcriptional and post-transcriptional regulation, as well as epigenetic modifications). Metabolic engineering strategies aimed at boosting isoflavonoid content in both leguminous and non-leguminous plants. Additionally, we discuss emerging technologies and resources for precise isoflavonoid regulation. This comprehensive review primarily focuses on model plants and crops, offering insights for more effective and sustainable metabolic engineering approaches to enhance nutritional quality and stress tolerance.

The putative ABCG transporter VviABCG20 from grapevine (Vitis vinifera) is strongly expressed in the seed coat of developing seeds and may participate in suberin biosynthesis

Half-size ATP binding cassette G (ABCG) transporters participate in many biological processes by transporting specific substrates. Our previous study showed that VviABCG20 was strongly expressed in the seeds of seeded grape and the silencing of VviABCG20 homolog gene in tomato led to a reduction in seed number. To reveal the molecular mechanism of VviABCG20 gene involved in grape seed development/abortion, the gene expression and functional analysis of VviABCG20 were further carried out in the grapevine. It was shown that the gene expression of VviABCG20 was higher in seeds of seeded grapes compared with seedless. Further the expression of VviABCG20 in the seed coat was significantly higher than in ovules (young seeds) and endosperm. VviABCG20 was also induced by exogenous hormones (especially MeJA) in grape leaves. Subcellular localization analysis showed that VviABCG20 is a membrane protein. In overexpressed VviABCG20 transgenic callus of Thompson seedless, expression of genes GPAT5, FAR1 and FAR5 was increased significantly. After treatment with suberin precursors, the transgenic callus reduced the sensitivity to three cinnamic acid derivatives (cis-ferulic acid, caffeic acid, coumaric acid), succinic acid, and glycerol. In suspension cells, expression of VviABCG20 was increased significantly after treatment with suberin precursors. Our research suggested that VviABCG20 may function in seed development in grapevine, at least in part by participating in suberin biosynthesis in the seed coat.

Filling the Gap: Functional Clustering of ABC Proteins for the Investigation of Hormonal Transport in planta

Plant hormones regulate a myriad of plant processes, from seed germination to reproduction, from complex organ development to microelement uptake. Much has been discovered on the factors regulating the activity of phytohormones, yet there are gaps in knowledge about their metabolism, signaling as well as transport. In this review we analyze the potential of the characterized phytohormonal transporters belonging to the ATP-Binding Cassette family (ABC proteins), thus to identify new candidate orthologs in model plants and species important for human health and food production. Previous attempts with phylogenetic analyses on transporters belonging to the ABC family suggested that sequence homology per se is not a powerful tool for functional characterization. However, we show here that sequence homology might indeed support functional conservation of characterized members of different classes of ABC proteins in several plant species, e.g., in the case of ABC class G transporters of strigolactones and ABC class B transporters of auxinic compounds. Also for the low-affinity, vacuolar abscisic acid (ABA) transporters belonging to the ABCC class we show that localization-, rather than functional-clustering occurs, possibly because of sequence conservation for targeting the tonoplast. The ABC proteins involved in pathogen defense are phylogenetically neighboring despite the different substrate identities, suggesting that sequence conservation might play a role in their activation/induction after pathogen attack. Last but not least, in case of the multiple lipid transporters belong to different ABC classes, we focused on ABC class D proteins, reported to transport/affect the synthesis of hormonal precursors. Based on these results, we propose that phylogenetic approaches followed by transport bioassays and in vivo investigations might accelerate the discovery of new hormonal transport routes and allow the designing of transgenic and genome editing approaches, aimed to improve our knowledge on plant development, plant-microbe symbioses, plant nutrient uptake and plant stress resistance.

Molecular Characterization of LjSWEET3, a Sugar Transporter in Nodules of Lotus japonicus

Symbiotic nitrogen fixation in legumes contributes greatly to the global nitrogen cycle on the earth. In nodules, resident rhizobia supply nitrogen nutrient fixed from atmospheric N2 to the host plant; in turn, the plant provides photosynthetic metabolites to bacteroids as a carbon source. In this process, various transporters are involved at different membrane systems; however, little is known at the molecular level about the flow of carbon from the host cells to the symbiotic bacteria. We have been studying transporters functioning in nodules of Lotus japonicus, and found that out of 13 SWEET genes in the L. japonicus genome LjSWEET3, a member of the SWEET transporter family, is highly expressed in nodules. The SWEET family was first identified in Arabidopsis, where members of the family are involved in phloem loading, nectar secretion, pollen nutrition and seed filling. The expression of LjSWEET3 strongly increased during nodule development and reached the highest level in mature nodules. Histochemical analysis using L. japonicus plants transformed with LjSWEET3 promoter:GUS (β-glucuronidase) showed strong expression in the vascular systems of nodules. Analysis of an LjSWEET3-green fluorescent protein (GFP) fusion expressed in Nicotiana banthamiana and Coptis japonica indicates that LjSWEET3 localizes to the plasma membrane. Together these data are consistent with a role for LjSWEET3 in sugar translocation towards nodules and also suggest the possible existence of multiple routes of carbon supply into nodules.