Theindicaandjaponicarice (Oryza sativa) subspecies differ in nitrate (NO₃⁻) assimilation capacity and nitrogen (N) use efficiency (NUE). Here, we show that a major component of this difference is conferred by allelic variation atOsNR2, a gene encoding a NADH/NADPH-dependent NO₃⁻reductase (NR). Selection-driven allelic divergence has resulted in variantindicaandjaponica OsNR2alleles encoding structurally distinct OsNR2 proteins, withindicaOsNR2 exhibiting greater NR activity.Indica OsNR2also promotes NO₃⁻uptake via feed-forward interaction withOsNRT1.1B, a gene encoding a NO₃⁻uptake transporter. These properties enableindica OsNR2to confer increased effective tiller number, grain yield and NUE onjaponicarice, effects enhanced by interaction with an additionally introgressedindica OsNRT1.1Ballele. In consequence,indica OsNR2provides an important breeding resource for the sustainable increases injaponicarice yields necessary for future global food security.

Nitrogen (N) is a macronutrient that boosts carbon (C) metabolism and plant growth leading to biomass accumulation. The molecular connection between nitrogen utilization efficiency (NUE) and biomass production remains unclear. Here, via quantitative trait loci analysis and map-based cloning, we reveal that natural variation at the MYB61 locus leads to differences in N use and cellulose biogenesis between indica and japonica subspecies of rice. MYB61, a transcriptional factor that regulates cellulose synthesis, is directly regulated by a known NUE regulator GROWTH-REGULATING FACTOR4 (GRF4), which coordinates cellulosic biomass production and N utilization. The variation at MYB61 has been selected during indica and japonica domestication. The indica allele of MYB61 displays robust transcription resulting in higher NUE and increased grain yield at reduced N supply than that of japonica. Our study hence unravels how C metabolism is linked to N uptake and may provide an opportunity to reduce N use for sustainable agriculture.

Chlorophyll (Chl) b is a ubiquitous accessory pigment in land plants, green algae, and prochlorophytes. This pigment is synthesized from Chl a by chlorophyllide a oxygenase and plays a key role in adaptation to various environments. This study characterizes a rice mutant, pale green leaf (pgl), and isolates the gene PGL by using a map-based cloning approach. PGL, encoding chlorophyllide a oxygenase 1, is mainly expressed in the chlorenchyma and activated in the light-dependent Chl synthesis process. Compared with wild-type plants, pgl exhibits a lower Chl content with a reduced and disorderly thylakoid ultrastructure, which decreases the photosynthesis rate and results in reduced grain yield and quality. In addition, pgl exhibits premature senescence in both natural and dark-induced conditions and more severe Chl degradation and reactive oxygen species accumulation than does the wild-type. Moreover, pgl is sensitive to heat stress.

The karrikin signaling complex D14L-D3-OsSMAX1 acts parallel to and additively with the strigolactone signaling complex D14-D3-D53 to regulate rice mesocotyl el

The LARGE1/LARGE1/Mei2-Like protein4 (OML4), which is phosphorylated by GSK2, negatively regulates grain size and weight in rice.