Plant Biotechnology Journal最新文献

Resistant starch (RS) is a special kind of starch with beneficial effects on obesity, type 2 diabetes and other chronic complications. Breeding high-RS rice varieties is considered a valuable way to improve public health. However, most rice cultivars only contain an RS level lower than 2% in cooked rice, and cloning of RS genes is critical to improve RS levels in rice. The loss of function of Starch Synthases IIIa (SSIIIa) and SSIIIb, two amylopectin biosynthetic genes, could elevate RS levels up to 10%. Here, we performed a systematic genetic study of 14 amylopectin biosynthetic genes in the ssIIIa ssIIIb double mutant via genome editing, and investigated their effects on RS formation, the eating quality and grain yield. The results showed that deficiency in SSIIa, SSIVb or ISA2 under the ssIIIa ssIIIb background could each elevate RS content to above 14%, and the quadruple mutants of sbeI sbeIIb ssIIIa ssIIIb and sbeI ssIVb ssIIIa ssIIIb could further increase RS levels to over 18%. Furthermore, the eating quality of cooked rice and grain yield decreased along with the elevated RS contents, showing a trade-off among these traits. In these mutants, ssIIIa ssIIIb showed the balanced performance of RS and grain yield. This study provides insights into RS biosynthesis with a series of RS genes in the amylopectin biosynthesis pathway and practical strategy to breed high-RS rice varieties with balanced performance.

Very-long-chain (VLC) alkanes are major components of hydrophobic cuticular waxes that cover the aerial epidermis of land plants, serving as a waterproofing barrier to protect the plant against environmental stresses. The mechanism of VLC-alkane biosynthesis has been extensively elucidated in plants. However, little is known about the biosynthesis of long-chain alkanes (LC, C₁₃ ~ C₁₉) such as pentadecane in plants. Alkanes with different chain lengths are also major constituents of fossil fuels and thus the discovery of the alkane biosynthetic machinery in plants would provide a toolbox of enzymes for the production of renewable hydrocarbon sources and next generations of biofuels. The top leaves of Pogostemon cablin at young stage accumulate large amounts of LC-alkane pentadecane, making this plant an excellent system for the elucidation of LC-alkane biosynthetic machinery in plant. We show here that LC-alkane pentadecane biosynthesis in P. cablin involves an endoplasmic reticulum (ER)-localized complex made of PcCER1-LIKE3 and PcCER3, homologues of Arabidopsis ECERIFERUM1 (AtCER1) and AtCER3 proteins that are involved in Arabidopsis VLC-alkane biosynthesis. We reconstitute the biosynthesis of pentadecane in Nicotiana benthamiana by co-expression of PcCER1-LIKE3 and PcCER3 and further improve its production by silencing multifunctional acetyl-CoA carboxylases involved in fatty acid elongation pathway. Taken together, we uncovered the key biosynthetic machinery of LC-alkane pentadecane in P. cablin and demonstrated that using these newly identified enzymes to engineer this LC-alkane for liquid biofuel production in a heterologous plant host is possible.

Tomato is one of the most economically important vegetable crops in the world and has been seriously affected by the devastating agricultural pest root-knot nematodes (RKNs). Current understanding of tomato resistance to RKNs is quite limited. VQ motif-containing family proteins are plant-specific regulators; however, whether and how tomato VQs regulate resistance to RKNs is unknown. Here, we found that SlVQ15 recruited SlWRKY30IIc to coordinately control tomato defence against the RKN Meloidogyne incognita without affecting plant growth and productivity. The jasmonate (JA)-ZIM domain (JAZ) repressors of the phytohormone JAs signalling associated and interfered with the interaction of SlVQ15 and SlWRKY30IIc. In turn, SlWRKY30IIc bound to SlJAZs promoters and cooperated with SlVQ15 to repress their expression, whereas this inhibitory effect was antagonized by SlJAZ5, forming a feedback regulatory mechanism. Moreover, SlWRKY30IIc expression was directly regulated by SlMYC2, a SlJAZ-interacting negative regulator of resistance to RKNs. In conclusion, our findings revealed that a regulatory circuit of SlVQ15-SlWRKY30IIc and the JA pathway fine-tunes tomato defence against the RKN M. incognita, and provided candidate genes and clues with great potential for crop improvement.

It is urgent to mine novel blast-resistant genes in rice and develop new rice varieties with pyramiding blast-resistant genes. In this study, a new blast-resistant gene, OsBRW1, was screened from a set of rice near-isogenic lines (NILs) with different blast-resistant ability. Under the infection of Magnaporthe oryzae (M. oryzae), OsBRW1 in the resistant NIL Pi-4b was highly induced than that in the susceptible NIL Pi-1 and their parent line CO39, and the blast-resistant ability of OsBRW1 was further confirmed by using CRISPR/Cas9 knockout and over-expression methods. The protein encoded by OsBRW1 was a typical NBS-LRR with NB-ARC domain and localized in both cytoplasm and nucleus, and the transient expression of OsBRW1 was capable of triggering hypersensitive response in tobacco leaves. Protein interaction experiments showed that OsBRW1 protein directly interacted with OsSRFP1. At the early infection stage of M. oryzae, OsBRW1 gene induced OsSRFP1 to highly expression level and accumulated H₂O₂, up-regulated the defence responsive signalling transduction genes and the pathogenesis-related genes and increased JA and SA content in the resistant NIL Pi-4b. By contrary, lower content of endogenous JA and SA in osbrw1 mutants was found at the same stage. After that, OsSRFP1 was down-regulated to constitution abundance to balance the growth of the resistant NIL Pi-4b. In summary, OsBRW1 solicited OsSRFP1 to resist the infection of blast fungus in rice by inducing the synergism of induced systemic resistance (ISR) and system acquired resistance (SAR) and to balance the growth of rice plants.

Heat stress (HS) has become a major factor limiting crop yields worldwide. HS inhibits plant growth by ROS accumulation, and NADPH oxidases (Rbohs) are major ROS producers in plants. Here, we show that CRISPR/Cas knockout of the OsRbohB (OsRbohB-KO) significantly increased rice tolerance to HS imposed at various different growth stages. We produced OsRbohB-KO and OsRbohB-overexpression (OsRbohB-OE) lines in a japonica cultivar, Nipponbare. Compared with nontransgenic wild-type (WT) plants, the OsRbohB-KO lines showed a significant increase in chlorophyll contents (5.2%-58.0%), plant growth (48.2%-65.6%) and grain yield (8.9%-20.5%), while reducing HS-induced ROS accumulation in seeds (21.3%-33.0%), seedlings (13.0%-30.4%), anthers (13.1%-20.3%) and grains (9.7%-22.1%), under HS conditions. Analysis of yield components revealed that the increased yield of OsRbohB-KO plants was due to increased starch synthetase activity, spikelets per panicle (2.0%-9.3%), filled spikelets (4.8%-15.5%), percentage of filled spikelets (2.4%-6.8%) and 1000-grain weight (2.9%-7.4%) under HS conditions during the reproductive stage. Grain milling and appearance quality, and starch content were also significantly increased in OsRbohB-KO plants under HS conditions during the mature stage. Furthermore, OsRbohB-KO significantly upregulated the expression levels of heat shock-related genes, OsHSP23.7, OsHSP17.7, OsHSF7 and OsHsfA2a, in rice seedlings and grains under long-term HS conditions. Conversely, OsRbohB-OE resulted in phenotypes that were opposite to OsRbohB-KO in most cases. Our results suggest that suppression of OsRbohB provides an effective approach for alleviating heat damage and improving grain yield and quality of rice under long-term HS conditions.

The growing demand for sustainable platforms for biomolecule manufacturing has fuelled the development of plant-based production systems. Agroinfiltration, the current industry standard, offers several advantages but faces limitations for large-scale production due to high operational costs and batch-to-batch variability. Alternatively, here, we describe the CuBe system, a novel bean yellow dwarf virus (BeYDV)-derived conditional replicative expression platform stably transformed in Nicotiana benthamiana and activated by copper sulphate (CuSO₄), an inexpensive and widely used agricultural input. The CuBe system utilizes a synthetic circuit of four genetic modules integrated into the plant genome: (i) a replicative vector harbouring the gene of interest (GOI) flanked by cis-acting elements for geminiviral replication and novelly arranged to enable transgene transcription exclusively upon formation of the circular replicon, (ii) copper-inducible Rep/RepA proteins essential for replicon formation, (iii) the yeast-derived CUP2-Gal4 copper-responsive transcriptional activator for Rep/RepA expression, and (iv) a copper-inducible Flp recombinase to minimize basal Rep/RepA expression. CuSO₄ application triggers the activation of the system, leading to the formation of extrachromosomal replicons, expression of the GOI, and accumulation of the desired recombinant protein. We demonstrate the functionality of the CuBe system in N. benthamiana plants expressing high levels of eGFP and an anti-SARS-CoV-2 antibody upon copper treatment. Notably, the system is functional in post-harvest applications, a strategy with high potential impact for large-scale biomanufacturing. This work presents the CuBe system as a promising alternative to agroinfiltration for cost-effective and scalable production of recombinant proteins in plants.