Plant Physiology最新文献

Acetyl-CoA is the main substrate of lipid metabolism and functions as an energy source for plant development. In the cytoplasm, acetyl-CoA is mainly produced by ATP-citrate lyase (ACL), which is composed of ACLA and ACLB subunits. In this study, we isolated the restorer-4 (res4) of the thermo-sensitive genic male sterile mutant reversible male sterile-2 (rvms-2) in Arabidopsis (Arabidopsis thaliana). RES4 encodes ACLB1, and res4 harbors a point mutation (Gly584 to Arg) in the citryl-CoA lyase domain. Both the ACLA and ACLB subunits are expressed in the tapetal layer of anthers. RES4 is regulated by MS188, and the res4 point mutation leads to pollen with a defective exine structure. In res4, lipid accumulation was significantly reduced within the tapetum and locules. These results indicate that acetyl-CoA synthesized by ACL is used for sporopollenin biosynthesis in the tapetum. Microspore diameter was significantly smaller in res4 than in wild type, indicating that acetyl-CoA from the tapetum supplies microspore development. Previous studies have shown that delayed degradation of the tetrad wall in res2 and res3 provides additional protection for rvms-2 microspores. The reduced volume of res4 microspores may lessen the requirement for cell wall protection to restore rvms-2 fertility. This study reveals the function of ACL in anther development and the mechanisms of fertility restoration in photoperiod- and thermo-sensitive genic male sterile lines.

Phenylalanine metabolism serves as an important route for the production of diverse secondary metabolites including phenylpropanoids. The phenylpropanoid pathway is involved in plant immunity, but whether it can regulate rhizobacteria-induced resistance is poorly understood. In this study, we confirmed a growth-promoting rhizobacterium strain JR48 could induce resistance, strengthen salicylic acid (SA) signaling, and increase lignin content during Phytophthora capsici infection. We conducted transcriptome sequencing to analyze the effect of JR48 on the expression of pepper (Capsicum annuum L.) genes, generated transgenes and loss-of-function genetic materials to specify the function of peroxidase genes, and implemented metabolomics analysis to uncover the resistance-inducing metabolites of JR48. JR48 activated expression of several pepper peroxidase genes in the phenylpropanoid pathway during pathogen infection. These peroxidases positively regulated lignification-mediated pathogen resistance, and the phenylpropanoid pathway acted downstream of SA signaling to confer JR48-induced resistance. Further, JR48 was capable of producing phenylpyruvate to enhance phenylalanine accumulation, thereby reinforcing phenylalanine metabolism-dependent lignification and resistance. Our results revealed that JR48 produces phenylpyruvate to refuel phenylalanine metabolism and reinforces SA signaling to further activate expression of peroxidase genes. This study uncovers immune components previously hidden in metabolic pathways and a recent mechanism underlying rhizobacteria-induced plant resistance.

Ensuring an adequate food supply and enough energy to sustainably support future global populations will require enhanced productivity from plants. Oilseeds can help address these needs; but the fatty acid composition of seed oils is not always optimal, and higher yields are required to meet growing demands. Quantitative approaches including metabolic flux analysis can provide insights on unexpected metabolism (i.e. when metabolism is different than in a textbook) and can be used to guide engineering efforts; however, as metabolism is context specific, it changes with tissue type, local environment, and development. This review describes recent insights from metabolic flux analysis in oilseeds and indicates engineering opportunities based on emerging topics and developing technologies that will aid quantitative understanding of metabolism and enable efforts to produce more oil. We also suggest that investigating the key regulators of fatty acid biosynthesis, such as transcription factors, and exploring metabolic signals like phytohormones in greater depth through flux analysis could open new pathways for advancing genetic engineering and breeding strategies to enhance oil crop production.

Engineering plant vegetative tissue to accumulate triacylglycerols (TAG, e.g. oil) can increase the amount of oil harvested per acre to levels that exceed current oilseed crops. Engineered tobacco (Nicotiana tabacum) lines that accumulate 15% to 30% oil of leaf dry weight resulted in starkly different metabolic phenotypes. In-depth analysis of the leaf lipid accumulation and 14CO2 tracking describe metabolic adaptations to the leaf oil engineering. An oil-for-membrane lipid tradeoff in the 15% oil line (referred to as HO) was surprisingly not further exacerbated when lipid production was enhanced to 30% (LEAFY COTYLEDON 2 (LEC2) line). The HO line exhibited a futile cycle that limited TAG yield through exchange with starch, altered carbon flux into various metabolite pools and end products, and suggested interference of the glyoxylate cycle with photorespiration that limited CO2 assimilation by 50%. In contrast, inclusion of the LEC2 transcription factor in tobacco improved TAG stability, alleviated the TAG-to-starch futile cycle, and recovered CO2 assimilation and plant growth comparable to wild type but with much higher lipid levels in leaves. Thus, the unstable production of storage reserves and futile cycling limit vegetative oil engineering approaches. The capacity to overcome futile cycles and maintain enhanced stable TAG levels in LEC2 demonstrated the importance of considering unanticipated metabolic adaptations while engineering vegetative oil crops.