Starch biosynthesis is a complex process that relies on the coordinated action of multiple enzymes.  Resistant starch is not digested in the small intestine, thus preventing a rapid rise in the glycemic index.  Starch synthase 2a (SS2a) is a key enzyme in amylopectin biosynthesis that has significant effects on starch structure and properties.  In this study, we identified an ss2a null mutant (M3-1413) with a single base mutation from an ethyl methane sulfonate (EMS)-mutagenized population of barley.  The mutation was located at the 3´ end of the first intron of the RNA splicing receptor (AG) site, and resulted in abnormal RNA splicing and two abnormal transcripts of ss2a, which caused the inactivation of the SS2a gene.  The starch structure and properties were significantly altered in the mutant, with M3-1413 containing lower total starch and higher amylose and resistant starch levels.  This study sheds light on the effect of barley ss2a null mutations on starch properties and will help to guide new applications of barley starch in the development of nutritious food products.

The flesh color of pummelo (Citrus maxima) fruits is highly diverse and largely depends on the level of carotenoids, which are beneficial to human health.  It is vital to investigate the regulatory network of carotenoid biosynthesis to improve the carotenoid content in pummelo.  However, the molecular mechanism underlying carotenoid accumulation in pummelo is not fully understood.  In this study, we identified a novel histone methyltransferase gene, CgSDG40, involved in carotenoid regulation by analyzing the flesh transcriptome of typical white-fleshed pummelo, red-fleshed pummelo and extreme-colored F₁ hybrids from a segregated pummelo population.  Expression of CgSDG40 corresponded to flesh color change and was highly coexpressed with CgPSY1.  Interestingly, CgSDG40 and CgPSY1 are located physically adjacent to each other on the chromosome in opposite directions, sharing a partially overlapping promoter region.  Subcellular localization analysis indicated that CgSDG40 localizes to the nucleus.  Overexpression of CgSDG40 significantly increased the total carotenoid content in citrus calli relative to that in wild type.  In addition, expression of CgPSY1 was significantly activated in overexpression lines relative to wild type.  Taken together, our findings reveal a novel histone methyltransferase regulator, CgSDG40, involved in the regulation of carotenoid biosynthesis in citrus and provide new strategies for molecular design breeding and genetic improvement of fruit color and nutritional quality.

Nitrogen (N) significantly affects rice yield and lodging resistance.  Previous studies have primarily investigated the impact of N management on rice lodging in conventional rice monoculture (RM); however, few studies have performed such investigations in rice–crayfish coculture (RC).  We hypothesized that RC would increase rice lodging risk and that optimizing N application practices would improve rice lodging resistance without affecting food security.  We conducted a two-factor (rice farming mode and N management practice) field experiment from 2021 to 2022 to test our hypothesis.  The rice farming modes included RM and RC, and the N management practices included no nitrogen fertilizer, conventional N application, and optimized N treatment.  The rice yield and lodging resistance characteristics, such as morphology, mechanical and chemical characteristics, anatomic structure, and gene expression levels, were analyzed and compared among the treatments.  Under the same N application practice, RC decreased the rice yield by 11.1–24.4% and increased the lodging index by 19.6–45.6% compared with the values yielded in RM.  In RC, optimized N application decreased the plant height, panicle neck node height, center of gravity height, bending stress, and lodging index by 4.0–4.8%, 5.2–7.8%, 0.5–4.5%, 5.5–10.5%, and 1.8–19.5%, respectively, compared with those in the conventional N application practice.  Furthermore, it increased the culm diameter, culm wall thickness, breaking strength, and non-structural and structural carbohydrate content by 0.8–4.9%, 2.2–53.1%, 13.5–19.2%, 2.2–24.7%, and 31.3–87.2%, respectively.  Optimized N application increased sclerenchymal and parenchymal tissue areas of the vascular bundle at the culm wall of the base second internode.  Furthermore, optimized N application upregulated genes involved in lignin and cellulose synthesis, thereby promoting lower internodes on the rice stem and enhancing lodging resistance.  Optimized N application in RC significantly reduced the lodging index by 1.8–19.5% and stabilized the rice yield (>8,570 kg ha^–1 on average).  This study systematically analyzed and compared the differences in lodging characteristics between RM and RC.  The findings will aid in the development of more efficient practices for RC that will reduce N fertilizer application.

Wampee (Clausena lansium) is an important evergreen fruit tree native to southern China that has a long history of use for medicinal purposes.  Here, a chromosome-level genome of C. lansium was constructed with a genome size of 282.9 Mb and scaffold N50 of 30.75 Mb.  The assembled genome contains 48.70% repetitive elements and 24,381 protein-coding genes.  Comparative genomic analysis showed that C. lansium diverged from Aurantioideae 15.91–24.95 million years ago.  Additionally, some expansive and specific gene families related to methyltransferase activity and S-adenosylmethionine-dependent methyltransferase activity were also identified.  Further analysis indicated that N-methyltransferase (NMT) is mainly involved in alkaloid biosynthesis and O-methyltransferase (OMT) participates in the regulation of coumarin accumulation in wampee.  This suggested that wampee’s richness in alkaloids and coumarins might be due to the gene expansions of NMT and OMT.  The tandem repeat event was one of the major reasons for the NMT expansion.  Hence, the reference genome of C. lansium will facilitate the identification of some useful medicinal compounds from wampee resources and reveal their biosynthetic pathways.