Carotenoid isomerase regulates rice tillering and grain productivity by its biosynthesis pathway.

Carotenoid isomerase activity and carotenoid content maintain the appropriate tiller number, photosynthesis, and grain yield. Interactions between the strigolactone and abscisic acid pathways regulates tiller formation.

Genetic Dissection of Panicle Morphology Traits in Super High-Yield Hybrid Rice Chaoyou 1000.

The morphological characteristics of the rice panicle play a pivotal role in influencing yield. In our research, we employed F2 and F2:3 populations derived from the high-yielding hybrid rice variety Chaoyou 1000. We screened 123 pairs of molecular markers, which were available, to construct the genetic linkage map. Subsequently, we assessed the panicle morphology traits of F2 populations in Lingshui County, Hainan Province, in 2017, and F2:3 populations in Hangzhou City, Zhejiang Province, in 2018. These two locations represent two types of ecology. Hangzhou's climate is characterized by high temperatures and humidity, while Lingshui's climate is characterized by a tropical monsoon climate. In total, 33 QTLs were identified, with eight of these being newly discovered, and two of them were consistently detected in two distinct environments. We identified fourteen QTL-by-environment interactions (QEs), which collectively explained 4.93% to 59.95% of the phenotypic variation. While most of the detected QTLs are consistent with the results of previous tests, the novel-detected QTLs will lay the foundation for rice yield increase and molecular breeding.

LAZY4 acts additively with the starch-statolith-dependent gravity-sensing pathway to regulate shoot gravitropism and tiller angle in rice.

Rice tiller angle is a key agronomic trait that has significant effects on the establishment of a high-yield rice population. However, the molecular mechanism underlying the control of rice tiller angle remains to be clarified. Here, we characterized the novel tiller-angle gene LAZY4 (LA4) in rice through map-based cloning. LA4 encodes a C3H2C3-type RING zinc-finger E3 ligase localized in the nucleus, and an in vitro ubiquitination assay revealed that the conserved RING finger domain is essential for its E3 ligase activity. We found that expression of LA4 can be induced by gravistimulation and that loss of LA4 function leads to defective shoot gravitropism caused by impaired asymmetric auxin redistribution upon gravistimulation. Genetic analysis demonstrated that LA4 acts in a distinct pathway from the starch biosynthesis regulators LA2 and LA3, which function in the starch-statolith-dependent pathway. Further genetic analysis showed that LA4 regulates shoot gravitropism and tiller angle by acting upstream of LA1 to mediate lateral auxin transport upon gravistimulation. Our studies reveal that LA4 regulates shoot gravitropism and tiller angle upstream of LA1 through a novel pathway independent of the LA2-LA3-mediated gravity-sensing mechanism, providing new insights into the rice tiller-angle regulatory network.