LATA1, a RING E3 ligase, modulates the tiller angle by affecting auxin asymmetric distribution and content in rice.

The tiller angle is an important agronomic trait that determines plant architecture and grain yield in rice (Oryza sativa L.). However, the molecular regulation mechanism of the rice tiller angle remains unclear. Here, we identified a rice tiller angle gene, LARGE TILLER ANGLE 1 (LATA1), using the MutMap approach. LATA1 encodes a C3H2C3-type RING zinc finger E3 ligase and the conserved region of the RING zinc finger is essential for its E3 activity. LATA1 was highly expressed in the root and tiller base and LATA1-GFP fusion protein was specifically localized to the nucleus. The mutation of LATA1 significantly reduced indole-3-acetic acid content and attenuated lateral auxin transport, thereby resulting in defective shoot gravitropism and spreading plant architecture in rice. Further investigations found that LATA1 may indirectly affect gravity perception by modulating the sedimentation rate of gravity-sensing amyloplasts upon gravistimulation. Our findings provide new insights into the molecular mechanism underlying the rice tiller angle and new genetic resource for the improvement of plant architecture in rice.

Identification of quantitative trait loci for important agronomic traits using chromosome segment substitution lines from a japonica × indica cross in rice.

Asian cultivated rice (Oryza sativa L.) has two subspecies, indica and japonica, which display clear differences in yield-related traits and environmental adaptation. Here, we developed a set of chromosome segment substitution lines (CSSLs) from an advanced backcross between japonica variety C418, as the recipient, and indica variety IR24, as the donor. Through evaluating the genotypes and phenotypes of 181 CSSLs, a total of 85 quantitative trait loci (QTLs) for 14 yield-related traits were detected, with individual QTLs explaining from 6.2 to 42.9% of the phenotypic variation. Moreover, twenty-six of these QTLs could be detected in the two trial sites (Beijing and Hainan). Among these loci, the QTLs for flag leaf width and effective tiller number, qFLW4.2 and qETN4.2, were delimited to an approximately 256-kb interval on chromosome 4. Through a comparison of nucleotide sequences and expression levels in "C418" and the CSSL CR31 containing qFLW4.2 and qETN4.2, we found that the NAL1 (LOC_Os04g52479) gene was the candidate gene for qFLW4.2 and qETN4.2. Our results show that CSSLs are powerful tools for identifying and fine-mapping QTLs, while the novel QTLs identified in this study will also provide new genetic resources for rice improvement. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-022-01343-3.

Whole-genome de novo assemblies reveal extensive structural variations and dynamic organelle-to-nucleus DNA transfers in African and Asian rice.

Asian cultivated rice (Oryza sativa) and African cultivated rice (Oryza glaberrima) originated from the wild rice species Oryza rufipogon and Oryza barthii, respectively. The genomes of both cultivated species have undergone profound changes during domestication. Whole-genome de novo assemblies of O. barthii, O. glaberrima, O. rufipogon and Oryza nivara, produced using PacBio single-molecule real-time (SMRT) and next-generation sequencing (NGS) technologies, showed that Gypsy-like retrotransposons are the major contributors to genome size variation in African and Asian rice. Through the detection of genome-wide structural variations (SVs), we observed that besides 28 shared SV hot spots, another 67 hot spots existed in either the Asian or African rice genomes. Based on gene annotation information of the SVs, we established that organelle-to-nucleus DNA transfers resulted in numerous SVs that participated in the nuclear genome divergence of rice species and subspecies. We detected 52 giant nuclear integrants of organelle DNA (NORGs, defined as >10 kb) in six Oryza AA genomes. In addition, we developed an effective method to genotype giant NORGs, based on genome assembly, and first showed the dynamic change in the distribution of giant NORGs in rice natural population. Interestingly, 16 highly differentiated giant NORGs tended to accumulate in natural populations of Asian rice from higher latitude regions, grown at lower temperatures and light intensities. Our study provides new insight into the genome divergence of African and Asian rice, and establishes that organelle-to-nucleus DNA transfers, as potentially powerful contributors to environmental adaptation during rice evolution, play a major role in producing SVs in rice genomes.