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Phosphorus is an essential macronutrient for plant development and metabolism, and plants have evolved ingenious mechanisms to overcome phosphate (Pi) starvation. However, the molecular mechanisms underlying the regulation of shoot and root architecture by low phosphorus conditions and the coordinated utilization of Pi and nitrogen remain largely unclear. Here, we show that Nodulation Signaling Pathway 1 (NSP1) and NSP2 regulate rice tiller number by promoting the biosynthesis of strigolactones (SLs), a class of phytohormones with fundamental effects on plant architecture and environmental responses. We found that NSP1 and NSP2 are induced by Oryza sativa PHOSPHATE STARVATION RESPONSE2 (OsPHR2) in response to low-Pi stress and form a complex to directly bind the promoters of SL biosynthesis genes, thus markedly increasing SL biosynthesis in rice. Interestingly, the NSP1/2–SL signaling module represses the expression of CROWN ROOTLESS 1 (CRL1), a newly identified early SL-responsive gene in roots, to restrain lateral root density under Pi deficiency. We also demonstrated that GR244DO treatment under normal conditions inhibits the expression of OsNRTs and OsAMTs to suppress nitrogen absorption but enhances the expression of OsPTs to promote Pi absorption, thus facilitating the balance between nitrogen and phosphorus uptake in rice. Importantly, we found that NSP1p : NSP1 and NSP2p : NSP2 transgenic plants show improved agronomic traits and grain yield under low- and medium-phosphorus conditions. Taken together, these results revealed a novel regulatory mechanism of SL biosynthesis and signaling in response to Pi starvation, providing genetic resources for improving plant architecture and nutrient-use efficiency in low-Pi environments. The molecular mechanisms underlying the regulation of shoot and root architecture by low phosphorus conditions remain largely unclear. This study reveals that NSP1 and NSP2, which are induced in response to low phosphorus, form a complex to promote the expression of strigolactone (SL) biosynthesis genes, dramatically increasing SL production and thereby repressing tiller and lateral root development in rice. Rational manipulation of NSP1 and NSP2 can improve agronomic traits and grain yield of rice under low- and moderate-phosphorus conditions. [ABSTRACT FROM AUTHOR]

N-terminal acetylation is one of the most common protein modifications in eukaryotes, and approximately 40% of human and plant proteomes are acetylated by ribosome-associated N-terminal acetyltransferase A (NatA) in a co-translational manner. However, the in vivo regulatory mechanism of NatA and the global impact of NatA-mediated N-terminal acetylation on protein fate remain unclear. Here, we identify Huntingtin Yeast partner K (HYPK), an evolutionarily conserved chaperone-like protein, as a positive regulator of NatA activity in rice. We found that loss of OsHYPK function leads to developmental defects in rice plant architecture but increased resistance to abiotic stresses, attributable to perturbation of the N-terminal acetylome and accelerated global protein turnover. Furthermore, we demonstrated that OsHYPK is also a substrate of NatA and that N-terminal acetylation of OsHYPK promotes its own degradation, probably through the Ac/N-degron pathway, which could be induced by abiotic stresses. Taken together, our findings suggest that the OsHYPK-NatA complex plays a critical role in coordinating plant development and stress responses by dynamically regulating NatA-mediated N-terminal acetylation and global protein turnover, which are essential for maintaining adaptive phenotypic plasticity in rice. N-terminal acetyltransferase A (NatA) acetylates approximately 40% of human and plant proteomes. This study reveals that OsHYPK acts as both a positive regulator and a substrate of NatA to coordinate plant development and stress responses by dynamically regulating NatA-mediated N-terminal acetylation and global protein turnover, thereby promoting adaptive phenotypic plasticity in rice. [ABSTRACT FROM AUTHOR]

Crop plant architecture is an important agronomic trait that contributes greatly to crop yield. Tiller angle is one of the most critical components that determine crop plant architecture, which in turn substantially affects grain yield mainly owing to its large influence on plant density. Gravity is a fundamental physical force that acts on all organisms on earth. Plant organs sense gravity to control their growth orientation, including tiller angle in rice (Oryza sativa). This review summarizes recent research advances made using rice tiller angle as a research model, providing insights into domestication of rice tiller angle, genetic regulation of rice tiller angle, and shoot gravitropism. Finally, we propose that current discoveries in rice can shed light on shoot gravitropism and improvement of plant tiller/branch angle in other species, thereby contributing to agricultural production in the future. Tiller angle is one of the most critical components that determine crop plant architecture and grain yield. Significant progress has been made in elucidating the molecular mechanisms that control tiller angle using rice as a model. This review focuses on discussing molecular regulation of rice tiller angle, whereas it may also be useful for the scientists studying lateral shoot orientation. [ABSTRACT FROM AUTHOR]

Grain number per panicle (GNP) is an important agronomic trait that contributes to rice grain yield. Despite its importance in rice breeding, the molecular mechanism underlying GNP regulation remains largely unknown. In this study, we identified a previously unrecognized regulatory gene that controls GNP in rice, Oryza sativa REPRODUCTIVE MERISTEM 20 (OsREM20), which encodes a B3 domain transcription factor. Through genetic analysis and transgenic validation we found that genetic variation in the CArG box-containing inverted repeat (IR) sequence of the OsREM20 promoter alters its expression level and contributes to GNP variation among rice varieties. Furthermore, we revealed that the IR sequence regulates OsREM20 expression by affecting the direct binding of OsMADS34 to the CArG box within the IR sequence. Interestingly, the divergent pOsREM20 IR and pOsREM20 ΔIR alleles were found to originate from different Oryza rufipogon accessions, and were independently inherited into the japonica and indica subspecies, respectively, during domestication. Importantly, we demonstrated that IR sequence variations in the OsREM20 promoter can be utilized for germplasm improvement through either genome editing or traditional breeding. Taken together, our study characterizes novel genetic variations responsible for GNP diversity in rice, reveals the underlying molecular mechanism in the regulation of agronomically important gene expression, and provides a promising strategy for improving rice production by manipulating the cis- regulatory element-containing IR sequence. OsREM20, a B3 domain transcription factor, acts as a key regulator of GNP in rice. Natural variation in the CArG box-containing inverted repeat (IR) sequence of OsREM20 promoter contributes to GNP variation among rice varieties. The IR sequence regulates OsREM20 expression by affecting the binding activity of OsMADS34, which could activate OsREM20 expression. [ABSTRACT FROM AUTHOR]

Rice tillering is an important agronomic trait affecting grain yield. Here, we identified a high-tillering mutant tillering20 (t20), which could be restored to the wild type by treatment with the strigolactone (SL) analog rac -GR24. T20 encodes a chloroplast ζ-carotene isomerase (Z-ISO), which is involved in the biosynthesis of carotenoids and their metabolites, SL and abscisic acid (ABA). The t20 mutant has reduced SL and ABA, raising the question of how SL and ABA biosynthesis is coordinated, and whether they have overlapping functions in tillering. We discovered that rac -GR24 stimulated T20 expression and enhanced all- trans -β-carotene biosynthesis. Importantly, rac -GR24 also stimulated expression of Oryza sativa 9-CIS-EPOXYCAROTENOID DIOXYGENASE 1 (OsNCED1) through induction of Oryza sativa HOMEOBOX12 (OsHOX12), promoting ABA biosynthesis in shoot base. On the other hand, ABA treatment significantly repressed SL biosynthesis and the ABA biosynthetic mutants displayed elevated SL biosynthesis. ABA treatment reduced the number of basal tillers in both t20 and wild-type plants. Furthermore, while ABA-deficient mutants aba1 and aba2 had the same number of basal tillers as wild type, they had more unproductive upper tillers at maturity. This work demonstrates complex interactions in the biosynthesis of carotenoid, SLs and ABA, and reveals a role for ABA in the regulation of rice tillering. Tillering is an important agronomic trait affecting grain yield. This study reveals that the high-tillering mutant, tillering20 , with reduced SL and ABA levels, was caused by defects in Z-ISO, a key enzyme in carotenoid biosynthesis. SLs promote ABA biosynthesis in the shoot base, whereas ABA inhibits SL biosynthesis, revealing a mechanism wherein SL and ABA biosynthesis are closely integrated to coordinately repress tillering in rice. [ABSTRACT FROM AUTHOR]

Tillering in rice is one of the most important agronomic traits. Rice tiller development can be divided into two main processes: the formation of the axillary bud and its subsequent outgrowth. Several genes critical for bud formation in rice have been identified by genetic studies; however, their molecular functions and relationships are still largely unknown. Here, we report that MONOCULM 1 (MOC1) and MONOCULM 3/TILLERS ABSENT 1/STERILE AND REDUCED TILLERING 1 (MOC3/TAB1/SRT1), two vital regulators for tiller formation in rice, physically interact to regulate tiller bud outgrowth through upregulating the expression of FLORAL ORGAN NUMBER1 (FON1), the homolog of CLAVATA1 in rice. We found that MOC3 is able to directly bind the promoter of FON1 and subsequently activate FON1 expression. MOC1 functions as a co-activator of MOC3, whereas it could not directly bind the FON1 promoter, and further activated FON1 expression in the presence of MOC3. Accordingly, FON1 is highly expressed at axillary meristems and shows remarkably decreased expression levels in moc1 and moc3 mutants. Loss-of-function mutants of FON1 exhibit normal bud formation but defective bud outgrowth and reduced tiller number. Collectively, these results shed light on a joint transcriptional regulatory mechanim by MOC1 and MOC3, and establish a new framework for the control of tiller bud formation and outgrowth. MOC3 (OsWUS), an important rice tiller bud formation regulator, directly binds the promoter of FON1 (rice CLAVATA1 homolog) to activate its expression in axillary meristems and thus regulates tiller bud outgrowth, showing diverse WUS-CLV pathways between monocotyledonous and dicotyledonous plants. MOC1 interacts with MOC3 and functions as a co-activator to promote FON1 expression. [ABSTRACT FROM AUTHOR]

Rice tiller angle is a key agronomic trait that contributes to ideal plant architecture and grain production. LAZY1 (LA1) was previously shown to control tiller angle via affecting shoot gravitropism, but the underlying molecular mechanism remains largely unknown. In this study, we identified an LA1-interacting protein named Brevis Radix Like 4 (OsBRXL4). We showed that the interaction between OsBRXL4 and LA1 occurs at the plasma membrane and that their interaction determines nuclear localization of LA1. We found that nuclear localization of LA1 is essential for its function, which is different from AtLA1, its Arabidopsis ortholog. Overexpression of OsBRXL4 leads to a prostrate growth phenotype, whereas OsBRXLs RNAi plants, in which the expression levels of OsBRXL1 , OsBRXL4 , and OsBRXL5 were decreased, display a compact phenotype. Further genetic analysis also supported that OsBRXL4 controls rice tiller angle by affecting nuclear localization of LA1. Consistently, we demonstrated that OsBRXL4 regulates the shoot gravitropism through affecting polar auxin transport as did LA1. Taken together, our study not only identifies OsBRXL4 as a regulatory component of rice tiller angle but also provides new insights into genetic regulation of rice plant architecture. In this study, Li et al. identified an LA1-interacting protein OsBRXL4, a member of the plant-specific Brevis Radix (BRX) family. The study further revealed that OsBRXL4 can interact with LA1 and affect nuclear localization of LA1, which is essential for the biological function of LA1 in controlling rice tiller angle. [ABSTRACT FROM AUTHOR]

Cultivated rice varieties are all diploid, and polyploidization of rice has long been desired because of its advantages in genome buffering, vigorousness, and environmental robustness. However, a workable route remains elusive. Here, we describe a practical strategy, namely de novo domestication of wild allotetraploid rice. By screening allotetraploid wild rice inventory, we identified one genotype of Oryza alta (CCDD), polyploid rice 1 (PPR1), and established two important resources for its de novo domestication: (1) an efficient tissue culture, transformation, and genome editing system and (2) a high-quality genome assembly discriminated into two subgenomes of 12 chromosomes apiece. With these resources, we show that six agronomically important traits could be rapidly improved by editing O. alta homologs of the genes controlling these traits in diploid rice. Our results demonstrate the possibility that de novo domesticated allotetraploid rice can be developed into a new staple cereal to strengthen world food security. • Establishing efficient transformation and genome editing system in allotetraploid rice • The high-quality assembly of the genome of allotetraploid rice • Identification of O. alta homologs of agronomically important genes from diploid rice • Achieved targeted improvement of various traits in O. alta through genome editing Li and colleagues developed a breeding route to de novo domestication of wild allotetraploid rice that provides a rational strategy for creating novel crops and generated a series of allotetraploid rice lines edited in domestication-related and agronomically important genes. [ABSTRACT FROM AUTHOR]

The ribosome-tethered N-terminal acetyltransferase A (NatA) acetylates 52% of soluble proteins in Arabidopsis thaliana. This co-translational modification of the N terminus stabilizes diverse cytosolic plant proteins. The evolutionary conserved Huntingtin yeast partner K (HYPK) facilitates NatA activity in planta, but in vitro, its N-terminal helix α1 inhibits human NatA activity. To dissect the regulatory function of HYPK protein domains in vivo, we genetically engineer CRISPR-Cas9 mutants expressing a HYPK fragment lacking all functional domains (hypk-cr1) or an internally deleted HYPK variant truncating helix α1 but retaining the C-terminal ubiquitin-associated (UBA) domain (hypk-cr2). We find that the UBA domain of HYPK is vital for stabilizing the NatA complex in an organ-specific manner. The N terminus of HYPK, including helix α1, is critical for promoting NatA activity on substrates starting with various amino acids. Consequently, deleting only 42 amino acids inside the HYPK N terminus causes substantial destabilization of the plant proteome and higher tolerance toward drought stress., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)