Increasing the oil yield is a major objective for oilseed crop improvement. Oil biosynthesis and accumulation are influenced by multiple genes involved in embryo and seed development. The leafy cotyledon1 (LEC1) is a master regulator of embryo development that also enhances the expression of genes involved in fatty acid biosynthesis. We speculated that seed oil could be increased by targeted overexpression of a master regulating transcription factor for oil biosynthesis, using a downstream promoter for a gene in the oil biosynthesis pathway. To verify the effect of such a combination on seed oil content, we made constructs with maize (Zea mays) ZmLEC1 driven by serine carboxypeptidase-like (SCPL17) and acyl carrier protein (ACP5) promoters, respectively, for expression in transgenic Arabidopsis thaliana and Camelina sativa. Agrobacterium-mediated transformation successfully generated Arabidopsis and Camelina lines that overexpressed ZmLEC1 under the control of a seed-specific promoter. This overexpression does not appear to be detrimental to seed vigor under laboratory conditions and did not cause observable abnormal growth phenotypes throughout the life cycle of the plants. Overexpression of ZmLEC1 increased the oil content in mature seeds by more than 20% in Arabidopsis and 26% in Camelina. The findings suggested that the maize master regulator, ZmLEC1, driven by a downstream seed-specific promoter, can be used to increase oil production in Arabidopsis and Camelina and might be a promising target for increasing oil yield in oilseed crops.0

It has been demonstrated that the phosphorylation pathway of L-serine (Ser) biosynthesis (PPSB) is very important in plant growth and development, but whether and how PPSB affects nitrogen metabolism and starch accumulation has not been fully elucidated. In this study, we took the energy plant duckweed (strain Lemna turionifera 5511) as the research object and used a stable genetic transformation system to heterologously over-expressing Arabidopsis AtPSAT1 (the gene encoding phosphoserine aminotransferase, the second enzyme of PPSB). Our results showed that, under nitrogen starvation, the transgenic plants grew faster, with higher values of Fv/Fm, rETR, and Y(II), as well as fresh and dry weight, than the wild-type. More promisingly, the accumulation of starch was also found to be significantly improved when over-expressing AtPSAT1 in the transgenic plants. qRT-PCR analysis results showed that the expression of genes related to nitrogen assimilation, carbon metabolism, and starch biosynthesis was up-regulated, while the expression of starch degradation-related genes was down-regulated by AtPSAT1 over-expression. We propose that the increased starch accumulation caused by AtPSAT1 over-expression may result from both elevated photosynthetic capacity and nitrogen utilization efficiency. This research sheds new light on the mechanism underlying the ability of PPSB to coordinate nitrogen and carbon metabolism, and provides a feasible way to improve starch production, that is, through engineering PPSB in crops.

Duckweeds are well known for their high accumulation of starch under stress conditions, along with inhibited growth. The phosphorylation pathway of serine biosynthesis (PPSB) was reported as playing a vital role in linking the carbon, nitrogen, and sulfur metabolism in this plant. The overexpression of AtPSP1, the last key enzyme of the PPSB pathway in duckweed, was found to stimulate the accumulation of starch under sulfur-deficient conditions. The growth- and photosynthesis-related parameters were higher in the AtPSP1 transgenic plants than in the WT. The transcriptional analysis showed that the expression of several genes in starch synthesis, TCA, and sulfur absorption, transportation, and assimilation was significantly up- or downregulated. The study suggests that PSP engineering could improve starch accumulation in Lemna turionifera 5511 by coordinating the carbon metabolism and sulfur assimilation under sulfur-deficient conditions.

Background: Black spot disease severely constrains Chinese cabbage production. Methods: To elucidate the defence mechanisms underlying this response, transcriptomic and metabolomic profiles were analysed in leaves of the Chinese cabbage line 904B at 24 h post-inoculation (hpi) with Alternaria brassicicola. In parallel, gene silencing and overexpression were conducted for BraPBL, an RLCK family member in Chinese cabbage. Results: The Chinese cabbage line 904B exhibited marked suppression of cytokinin and auxin signalling, coupled with enhanced expression of genes involved in ethylene and jasmonic acid signalling. Multiple secondary metabolites exhibited differential changes, specifically the sterol compound 4,4-dimethyl-5alpha-cholest-7-en-3beta-ol was significantly upregulated in the treatment group. These metabolites were primarily enriched in the indole alkaloid metabolism and glycerolipid metabolism pathways. Concurrently, BraPBL exhibits increasing expression with prolonged infection. BraPBL overexpression enhances resistance to black spot disease, whereas silencing reduces resistance. Subcellular localization confirmed BraPBL at the plasma membrane. Overexpression of BraPBL upregulates the reactive oxygen species-related gene RBOH and the signal transduction-related gene MEKK1, whilst simultaneously activating the JA pathway. Conclusions: Overall, 904B activates defence-related hormones while suppressing growth and development-related hormones during early infection. Secondary metabolites, particularly the sterol compound 4,4-dimethyl-5alpha-cholest-7-en-3beta-ol, play key roles in defence, and BraPBL functions as a black spot disease–related defence gene in Chinese cabbage.

Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) catalyzes the deamination of phenylalanine, which is the initial step in the biosynthesis of phenylpropanoids. It serves as a crucial enzyme that facilitates the transfer of carbon from primary to secondary metabolism in plants. Duckweed is regarded as a promising chassis plant in synthetic biology research and application, due to its being rich in secondary metabolites and other advantages. The genes encoding PAL in Spirodela polyrhiza (L.) Schleid, the giant duckweed, were investigated in this study. Three SpPAL genes (SpPAL1–SpPAL3) were identified and cloned. All of them were successfully expressed in E. coli, and their recombinant proteins all showed PAL activity. In addition, SpPAL1 and SpPAL2 proteins could also utilize tyrosine as substrate, although the activity was low. A qRT-PCR analysis demonstrated that the expression of SpPAL3 was most pronounced in young fronds. It was found that the expression of SpPAL1 and SpPAL3 was significantly induced by MeJA treatment. Overexpression of SpPAL3 in Lemna turionifera inhibited the growth of fronds and adventitious roots in the transgenic plants, indicating the importance of SpPAL3 in duckweed besides its involvement in the secondary metabolism.