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China’s food system is transforming from providing adequate and safe food to supplying nutritious and healthy food as the country develops into a new stage of comprehensive modernization. To be green and low-carbon has become the global consensus regarding food system transformation, and China plans to transform its food system to be inclusive and sharing. Currently, China’s food system faces multiple challenges such as the coexistence of overnutrition and nutritional deficiency, contradiction between supply assurance and carbon reduction, lack of tolerance for small-scale farmers and vulnerable groups of consumers, and weak resilience in production stability and supply controllability. Against the background of a declining population and an increasing urbanization rate, the structure of China’s food system needs to be further optimized and develops toward “nutrition and health, green and low carbon, inclusiveness and sharing, and safety and resilience”. Future efforts should focus on (1) adjusting the production system to enrich food supply, (2) strengthening scientific and technological innovation by prioritizing the development of win-win technologies, (3) improving relevant policies to increase investment in the transformation, (4) optimizing existing systems and mechanisms to build an efficient and inclusive food chain, and (5) promoting low-carbon consumption concepts and behaviors. Furthermore, we propose the following suggestions: (1) initiating nutrition-related legislation at the national level, (2) establishing a national reserve for food system transformation technologies, (3) launching a national science and technology project for food system transformation and upgrading, and (4) launching a national nutrition and health campaign.

Rice grain chalkiness is an important characteristic, but the difference between chalky and translucent parts in grains is still unclear. Here, we investigated the differences of flour made from the chalky or translucent part of rice grains in three indica and three japonica rice varieties. The chalky flour had significantly lower amylose and protein contents and looser starch granule morphology, and starches in the chalky flour had higher relative crystallinity, higher short chain content but lower long chain content than those in the translucent flour. The water states, determined with nuclear magnetic resonance, differed between the chalky and translucent flour after soaking, cooking and retrograding, and the chalky flour had more bound and free water but less constructural water than the translucent flour. Mostly, the chalky flour had lower viscosity and shorter gel consistency, but higher onset temperature and gelatinization enthalpy than the translucent flour. The results indicated that starch granule morphology would be more indicative than other attributions on pasting and gelatinization properties of chalky and translucent parts of rice grains.

NRL3 is essential for the growth and development of rice leaves. In this study, we found that the loss function of NRL3 also delayed heading date under natural long daylight and short daylight conditions. The yeast two-hybrid and the bimolecular fluorescence complementation proved that NRL3 interacts with OsK4, a Snf1-related kinase. OsK4 localized to the nucleus and expressed in various rice tissues. The rhythmic expression pattern of OsK4 was similar to NRL3 under long daylight and short daylight conditions. Knock-out mutants of OsK4 exhibited early heading under long daylight conditions, indicating that it acts as a negative regulator of heading date in rice. Interestingly, the OsK4 mutant under the nrl3 mutant background rescued the late heading phenotype of nrl3 under long daylight conditions, suggesting that OsK4 functions downstream of NRL3. Moreover, both NRL3 and OsK4 controlled heading date through regulating the expression of Hd3a and RFT1 genes. These findings shed light on the heading date regulation in rice and provide a sound theoretical base to improve regional adaptability of rice.

Summary: Rice tillering is one of the most important agronomical traits largely determining grain yield. Photosynthesis and nitrogen availability are two important factors affecting rice tiller bud elongation; however, underlying mechanism and their cross‐talk is poorly understood.Here, we used map‐based cloning, transcriptome profiling, phenotypic analysis, and molecular genetics to understand the roles of the Decreased Tiller Number 1 (DTN1) gene that encodes the fructose‐1,6‐bisphosphate aldolase and involves in photosynthesis required for light‐induced axillary bud elongation in rice.Deficiency of DTN1 results in the reduced photosynthetic rate and decreased contents of sucrose and other sugars in both leaves and axillary buds, and the reduced tiller number in dtn1 mutant could be partially rescued by exogenous sucrose treatment. Furthermore, we found that the expression of nitrogen‐mediated tiller growth response 5 (NGR5) was remarkably decreased in shoot base of dtn1‐2, which can be activated by sucrose treatment. Overexpression of NGR5 in the dtn1‐2 could partially rescue the reduced tiller number, and the tiller number of dtn1‐2 was insensitive to nitrogen supply.This work demonstrated that the sugar level regulated by photosynthesis and DTN1 could positively regulate NGR5 expression, which coordinates the cross‐talk between carbon and nitrate to control tiller bud outgrowth in rice. [ABSTRACT FROM AUTHOR]

A mechanized direct seeding of rice with less labor and water usage, has been widely adopted. However, this approach requires varieties that exhibit uniform seedling emergence. Mesocotyl elongation (ME) offers the main drive of fast emergence of rice seedlings from soils; nevertheless, its genetic basis remains unknown. Here, we identify a major rice quantitative trait locus Mesocotyl Elongation1 (qME1), an allele of the Green Revolution gene Semi‐Dwarf1 (SD1), encoding GA20‐oxidase for gibberellin (GA) biosynthesis. ME1 expression is strongly induced by soil depth and ethylene. When rice grains are direct‐seeded in soils, the ethylene core signaling factor OsEIL1 directly promotes ME1 transcription, accelerating bioactive GA biosynthesis. The GAs further degrade the DELLA protein SLENDER RICE 1 (SLR1), alleviating its inhibition of rice PHYTOCHROME‐INTERACTING FACTOR‐LIKE13 (OsPIL13) to activate the downstream expansion gene OsEXPA4 and ultimately promote rice seedling ME and emergence. The ancient traits of long mesocotyl and strong emergence ability in wild rice and landrace were gradually lost in company with the Green Revolution dwarf breeding process, and an elite ME1‐R allele (D349H) is found in some modern Geng varieties (long mesocotyl lengths) in northern China, which can be used in the direct seeding and dwarf breeding of Geng varieties. Furthermore, the ectopic and high expression of ME1 driven by mesocotyl‐specific promoters resulted in rice plants that could be direct‐seeded without obvious plant architecture or yield penalties. Collectively, we reveal the molecular mechanism of rice ME, and provide useful information for breeding new Green Revolution varieties with long mesocotyl suitable for direct‐seeding practice. [ABSTRACT FROM AUTHOR]

Summary: Head rice yield (HRY) measures rice milling quality and determines final grain yield and commercial value. Here, we report that two major quantitative trait loci for milling quality in rice, qMq‐1 and qMq‐2, represent allelic variants of Waxylv/Waxyb (hereafter Wx) encoding Granule‐Bound Starch Synthase I (GBSSI) and Alkali Spreading Value ALKc/ALKb encoding Soluble Starch Synthase IIa (SSIIa), respectively. Complementation and overexpression transgenic lines in indica and japonica backgrounds confirmed that Wx and ALK coordinately regulate HRY by affecting amylose content, the number of amylopectin branches, amyloplast size, and thus grain filling and hardness. The transcription factor OsDOF18 acts upstream of Wx and ALK by activating their transcription. Furthermore, rice accessions with Wxb and ALKb alleles showed improved HRY over those with Wxlv and ALKc. Our study not only reveals the novel molecular mechanism underlying the formation of HRY but also provides a strategy for breeding rice cultivars with improved HRY. [ABSTRACT FROM AUTHOR]

Isoamylase 1 (ISA1) is an isoamylase-type debranching enzyme which plays a predominant role in amylopectin synthesis. In this study, the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated endonuclease 9 (CRISPR/Cas9) system was used to edit ISA1 gene in rice via Agrobacterium-mediated transformation. We identified 36 genetic edited lines from 55 T0 transgenic events, and classified the mutation forms into 7 types. Of those, two homozygous mutants, cr-isa1-1 (type 1, with an adenine insertion) and cr-isa1-2 (type 3, with a cytosine deletion) were selected for further analysis. Seed sizes of both cr-isa1-1 and cr-isa1-2 were affected, and the two mutants also displayed a shrunken endosperm with significantly lower grain weight. Electron microscopy analysis showed that abnormal starch granules and amyloplasts were found in cr-isa1-1 and cr-isa1-2 endosperm cells. The contents of total starch, amylose and amylopectin in the endosperm of the cr-isa1 mutants were significantly reduced, whereas sugar content and starch gel consistency were observably increased compared to the wild-type. The gelatinization temperature and starch chain length distributions of the cr-isa1 mutants were also altered. Moreover, transcript levels of most starch synthesis-related genes were significantly lower in cr-isa1 mutants. In conclusion, the results indicated that gene edition of ISA1 affected starch synthesis and endosperm development, and brought potential implications for rice quality breeding. Keywords: ISA1, rice, starch biosynthesis, starch granule, physicochemical property, CRISPR, Cas9

High temperatures accelerate the accumulation of storage material in seeds, often leading to defects in grain filling. However, the mechanisms regulating grain filling at high temperatures remain unknown. Here, we want to explore the quality factors influenced by the environment and have identified a LATE EMBROYGENESIS ABUNDANT gene, OsLEA1b, a heat-stress-responsive gene in rice grain filling. OsLEA1b is highly expressed in the endosperm, and its coding protein localizes to the nucleus and cytoplasm. Knock-out mutants of OsLEA1b had abnormal compound starch granules in endosperm cells and chalky endosperm with significantly decreased grain weight and grain number per panicle. The oslea1b mutants exhibited a lower proportion of short starch chains with degrees of polymerization values from 6 to 13 and a higher proportion of chains with degrees from 14 to 48, as well as significantly lower contents of starch, protein, and lipid compared to the wild type. The difference was exacerbated under high temperature conditions. Moreover, OsLEA1b was induced by drought stress. The survival rate of oslea1b mutants decreased significantly under drought stress treatment, with significant increase in ROS levels. These results indicate that OsLEA1b regulates starch biosynthesis and influences rice grain quality, especially under high temperatures. This provides a valuable resource for genetic improvement in rice grain quality. [ABSTRACT FROM AUTHOR]