Production of grains with ultra-low heavy metal accumulation by pyramiding novel Alleles of OsNramp5 and OsLsi2 in two-line hybrid rice.

Ensuring rice yield and grain safety quality are vital for human health. In this study, we developed two-line hybrid rice (TLHR) with ultra-low grain cadmium (Cd) and arsenic (As) accumulation by pyramiding novel alleles of OsNramp5 and OsLsi2. We first generated low Cd accumulation restorer (R) lines by editing OsNramp5, OsLCD, and OsLCT in japonica and indica. After confirming that OsNramp5 was most efficient in reducing Cd, we edited this gene in C815S, a genic male sterile line (GMSL), and screened it for alleles with low Cd accumulation. Next, we generated R and GMSL lines with low As accumulation by editing OsLsi2 in a series of YK17 and C815S lines. When cultivated in soils that were heavily polluted with Cd and As, the edited R, GMSL, and TLHR plants showed significantly reduced heavy metal accumulation, while maintaining a relatively stable yield potential. This study provides an effective scheme for the safe production of grains in As- and/or Cd-polluted paddy fields.

The elite eating quality alleles Wxb and ALKb are regulated by OsDOF18 and coordinately improve head rice yield.

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.

Photosynthesis regulates tillering bud elongation and nitrogen-use efficiency via sugar-induced NGR5 in rice.

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.

Clinical Observation of Infarct Volume ≥150 mL in Endovascular Thrombectomy Treatment.

OBJECTIVES: Whether patients with infarct volume ≥150 mL could benefit from endovascular thrombectomy (EVT) remains unclear. METHODS: Patients (n=104) with anterior circulation Alberta Stroke Program Early Computed Tomography Score <6 were screened for infarct volume ≥150 mL using the Pullicino formula × (1-22%). The following were compared with the baseline at 90 days: the modified Rankin scale score (mRS) ≤3, mortality rate, symptomatic intracranial hemorrhage and any intracranial hemorrhage within 48 hours, and modified Thrombolysis in Cerebral Infarction (mTICI) ≥2b between the EVT and drug therapy (DT) groups. RESULTS: In patients with infarct volumes ≥150 mL, mRS≤3 at 90 days was higher in the EVT group than in the DT group [adjusted odds risk (aOR), 5.52; 95% CI: 1.10-28.24, P=0.04), and mTICI ≥2b at 82.8%. Intracranial hemorrhage within 48 hours occurred in 7 (24.1%) patients in the EVT group and 5 (14.7%) in the DT group (aOR, 0.75; 95% CI: 0.16-3.46; P=0.71). Older age (aOR, 0.94; 95% CI: 0.90-0.99, P=0.01), EVT treatment (aOR, 4.51; 95% CI: 1.60-12.78, P=0.01), and infarct volume ≥150 mL (aOR, 0.11; 95% CI: 0.04-0.31, P<0.01) were significantly associated with patient prognosis. CONCLUSIONS: Patients with infarct volume ≥150 mL who received EVT had a higher proportion of mRS≤3 compared with those who received DT. However, there was no statistically significant difference in intracranial hemorrhage and death between the groups. EVT, smaller infarct volume, and younger age were associated with a good prognosis. The findings require large sample data verification.

A mediator of OsbZIP46 deactivation and degradation negatively regulates seed dormancy in rice.

Preharvest sprouting (PHS) is a deleterious phenotype that occurs frequently in rice-growing regions where the temperature and precipitation are high. It negatively affects yield, quality, and downstream grain processing. Seed dormancy is a trait related to PHS. Longer seed dormancy is preferred for rice production as it can prevent PHS. Here, we map QTLs associated with rice seed dormancy and clone Seed Dormancy 3.1 (SDR3.1) underlying one major QTL. SDR3.1 encodes a mediator of OsbZIP46 deactivation and degradation (MODD). We show that SDR3.1 negatively regulates seed dormancy by inhibiting the transcriptional activity of ABIs. In addition, we reveal two critical amino acids of SDR3.1 that are critical for the differences in seed dormancy between the Xian/indica and Geng/japonica cultivars. Further, SDR3.1 has been artificially selected during rice domestication. We propose a two-line model for the process of rice seed dormancy domestication from wild rice to modern cultivars. We believe the candidate gene and germplasm studied in this study would be beneficial for the genetic improvement of rice seed dormancy.