Abstract Short dormancy period of sweetpotato (Ipomoea batatas) storage roots causes significant economic losses. To unravel the molecular mechanism of sweetpotato sprouting, a comparative transcriptome was performed using storage roots incubated under non-sprout (15 °C) and sprout favouring conditions (25 °C). Our analysis revealed that 7404 genes were differentially expressed between non-sprouting and sprouted storage roots incubated at 25 °C. Further, we observed that gibberellin (GA) biosynthesis gene IbGA3OXIDASE and abscisic acid (ABA) catabolism gene ABA 8'-HYDROXYLASE were upregulated by > 10-fold and > 40-fold, respectively, at the onset of sprouting. Metabolite profiling showed increased GA and cytokinin levels, but reduced ABA content in the sprout initials. Based on conserved expression patterns of phytohormone-related genes during sprouting in potato tubers and sweetpotato storage roots, two genes that were downregulated during sweetpotato sprouting - IbPYL4 (ABA receptor) and IbGA2OXIDASE (GA catabolic enzyme) - were independently overexpressed in potato. Transgenic potato plants overexpressing IbPYL4 or IbGA2OXIDASE exhibited low percentages of tuber sprouting and reduced sprout length. Furthermore, knockdown of the ABA 8'-HYDROXYLASE gene (ABA catabolism) significantly reduced sprout length in sweetpotato storage roots compared to wild-type plants. Overall, our study suggests that selective candidate genes (ABA 8'-HYDROXYLASE, IbPYL4, IbGA3OXIDASE, and IbGA2OXIDASE) could be targeted for developing sweetpotato genotypes with enhanced shelf-life.
Abstract Gibberellins (GAs) are widely used in grape cultivation to promote berry enlargement and induce seedlessness, but their effects on seed development and the regulatory mechanism remain poorly understood. In this study, exogenous GA3 significantly reduced seed weight in grapevine, indicating impaired seed development. To investigate the underlying mechanism, we characterized the grape DELLA protein SLENDER RICE 1 (VvSLR1). Overexpression of VvSLR1 in tomato caused a dwarf and compact phenotype but had limited effects on fruit and seed development under normal conditions. However, GA3 treatment caused a stronger reduction in seed formation in VvSLR1-overexpressing plants, whereas paclobutrazol (PAC), an inhibitor of GA biosynthesis, allowed relatively normal seed formation, indicating that the effect of VvSLR1 on reproductive development is GA-dependent. In grape calli, VvSLR1 overexpression altered GA metabolism and the expression of several VvGA20ox and VvGA3ox genes, suggesting a role for VvSLR1 in GA homeostasis. We further identified GAMETOPHYTE DEFECTIVE 1 (VvGAD1), whose Arabidopsis homolog is involved in gametophyte development, as a nuclear-localized VvSLR1-interacting protein. VvGAD1 associated with the promoter of GA 20-oxidase 4 (VvGA20ox4), and co-expression of VvGAD1 and VvSLR1 significantly enhanced VvGA20ox4 promoter activity. Moreover, heterologous expression of VvGA20ox4 in Arabidopsis increased silique length and seed number, while exogenous GA3 suppressed VvGA20ox4 promoter activity. Together, these findings suggest that VvSLR1 acts as a regulatory node linking GA signaling and homeostasis, with the VvSLR1-VvGAD1-VvGA20ox4 relationship representing a potential regulatory branch involved in GA-dependent seed development.
Abstract Betaine lipids (BLs) are a class of non-phosphorus glycerolipids widely found in microalgae, fungi, bacteria, mosses, and ferns. For decades, the central paradigm regarding the biological function of BLs has been their role in substituting for phospholipids under phosphate starvation—a crucial adaptive mechanism for survival in oligotrophic environments. However, accumulating evidence indicates that the functional diversity of BLs is far more extensive. Recent studies have demonstrated their distinct roles in fatty acid metabolism, adaptation to various environmental stresses, and ecological interactions such as symbiosis and predation. This review summarizes current insights into the pleiotropic roles of BLs in microalgal physiology and ecology, moving beyond their role as mere phospholipid surrogates. Furthermore, we highlight the recently discovered bioactive function of BL derivative in mammals.
Abstract Two isozymes of granule-bound starch synthase (GBSS), GBSSI and GBSSII, are present in rice. While GBSSI is solely responsible for amylose synthesis in endosperm and gbss1 mutants accumulate glutinous starch in grains, the role of GBSSII remains unclear. In this study, rice gbss2 mutants were isolated for the first time in cereals and gbss1 gbss2 double mutants were generated to clarify the respective roles of GBSS isozymes. Iodine staining of starch confirmed that amylose in pollen is synthesized by GBSSI and those in leaf and root tip are by GBSSII. Gel filtration chromatography of debranched starch from endosperm and leaf sheath revealed that GBSSI and GBSSII appear to be the primary amylose synthases in endosperm and in leaf sheath, respectively. However, the absence of the primary GBSS in the respective organs did not result in the complete elimination of amylose. A small peak detected in the fractions corresponding to amylose was shown to be α-glucans by glucoamylase digestion, and the presence of branches was revealed by detailed structure analyses. The amylose-like, branched α-glucans found in the double mutants, which probably also existed in single mutants and wild-type starches, were suggested to be synthesized by other enzymes than GBSSs.
Nitrogen availability is one of the main factors limiting crop productivity, and the low nitrogen use efficiency (NUE) of crops imposes significant economic and environmental costs. Research on NUE has traditionally focused on improving nitrogen uptake and assimilation; however, the efficient redistribution of assimilated nitrogen within the plant is equally important for growth, yield, and crop quality. Amino acids are the main form in which reduced nitrogen is transported over long distances. Their movement between source and sink tissues depends on a diverse group of membrane transporters belonging to the Amino Acid/Auxin Permeases (AAAP), Amino Acid/Polyamine/Choline transporters (APC), and Usually Multiple Acids Move In and Out Transporters (UMAMIT) families. These transporters mediate amino acid uptake, export, vascular loading and unloading, intracellular transport, and redistribution to developing organs, thereby influencing plant growth, reproductive development and the composition of harvested products. Recent work in cereals, legumes and horticultural crops has shown that modifying amino acid transport can alter biomass production, grain filling, seed protein content, fruit quality, and NUE. In this review, we summarize current knowledge of plant amino acid transporters, from their molecular and physiological functions to their roles in crop yield, nutritional quality and NUE. We also discuss how advances in genome editing, exploitation of natural genetic variation, high-throughput phenotyping and systems biology may facilitate the development of crops with more efficient nitrogen use and improved agricultural sustainability.
