RESUMO
Cell-to-cell communication precisely controls the creation of new organs during reproductive growth. However, the sensor molecules that mediate developmental signals in monocot plants are poorly understood. Here, we report that DWARF AND RUNTISH SPIKELET1 (DRUS1) and DRUS2, two closely related receptor-like kinases (RLKs), redundantly control reproductive growth and development in rice (Oryza sativa). A drus1-1 drus2 double knockout mutant, but not either single mutant, showed extreme dwarfism and barren inflorescences that harbored sterile spikelets. The gibberellin pathway was not impaired in this mutant. A phenotypic comparison of mutants expressing different amounts of DRUS1 and 2 revealed that reproductive growth requires a threshold level of DRUS1/2 proteins. DRUS1 and 2 maintain cell viability by repressing protease-mediated cell degradation and likely by affecting sugar utilization or conversion. In the later stages of anther development, survival of the endothecium requires DRUS1/2, which may stimulate expression of the UDP-glucose pyrophosphorylase gene UGP2 and starch biosynthesis in pollen. Unlike their Arabidopsis thaliana ortholog FERONIA, DRUS1 and 2 mediate a fundamental signaling process that is essential for cell survival and represents a novel biological function for the CrRLK1L RLK subfamily.
Assuntos
Metabolismo dos Carboidratos/genética , Oryza/genética , Proteínas de Plantas/genética , Receptores Proteína Tirosina Quinases/genética , Sequência de Aminoácidos , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Morte Celular/genética , Flores/enzimologia , Flores/genética , Flores/ultraestrutura , Perfilação da Expressão Gênica/métodos , Regulação da Expressão Gênica de Plantas , Immunoblotting , Hibridização In Situ , Microscopia Confocal , Microscopia Eletrônica , Oryza/enzimologia , Fosfotransferases/genética , Fosfotransferases/metabolismo , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Interferência de RNA , Receptores Proteína Tirosina Quinases/metabolismo , Reprodução/genética , Homologia de Sequência de Aminoácidos , Amido/metabolismoRESUMO
The palea and lemma are unique organs in grass plants that form a protective barrier around the floral organs and developing kernel. The interlocking of the palea and lemma is critical for maintaining fertility and seed yield in rice; however, the molecules that control the interlocking structure remain largely unknown. Here, we showed that when OsCR4 mRNA expression was knocked down in rice by RNA interference, the palea and lemma separated at later spikelet stages and gradually turned brown after heading, resulting in the severe interruption of pistil pollination and damage to the development of embryo and endosperm, with defects in aleurone. The irregular architecture of the palea and lemma was caused by tumour-like cell growth in the outer epidermis and wart-like cell masses in the inner epidermis. These abnormal cells showed discontinuous cuticles and uneven cell walls, leading to organ self-fusion that distorted the interlocking structures. Additionally, the faster leakage of chlorophyll, reduced silica content and elevated accumulation of anthocyanin in the palea and lemma indicated a lesion in the protective barrier, which also impaired seed quality. OsCR4 is an active receptor-like kinase associated with the membrane fraction. An analysis of promoter::GUS reporter plants showed that OsCR4 is specifically expressed in the epidermal cells of paleas and lemmas. Together, these results suggest that OsCR4 plays an essential role in maintaining the interlocking of the palea and lemma by promoting epidermal cell differentiation.
Assuntos
Diferenciação Celular , Oryza/enzimologia , Epiderme Vegetal/citologia , Proteínas de Plantas/metabolismo , Proteínas Quinases/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Técnicas de Silenciamento de Genes , Oryza/citologia , Oryza/genética , Epiderme Vegetal/crescimento & desenvolvimento , Infertilidade das Plantas , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas/citologia , Plantas Geneticamente Modificadas/enzimologia , Plantas Geneticamente Modificadas/genética , Proteínas Quinases/genética , Interferência de RNARESUMO
Plant architecture is determined by genetic and developmental programs as well as by environmental factors. Sessile plants have evolved a subtle adaptive mechanism that allows them to alter their growth and development during periods of stress. Phytohormones play a central role in this process; however, the molecules responsible for integrating growth- and stress-related signals are unknown. Here, we report a gain-of-function rice (Oryza sativa) mutant, tld1-D, characterized by (and named for) an increased number of tillers, enlarged leaf angles, and dwarfism. TLD1 is a rice GH3.13 gene that encodes indole-3-acetic acid (IAA)-amido synthetase, which is suppressed in aboveground tissues under normal conditions but which is dramatically induced by drought stress. The activation of TLD1 reduced the IAA maxima at the lamina joint, shoot base, and nodes, resulting in subsequent alterations in plant architecture and tissue patterning but enhancing drought tolerance. Accordingly, the decreased level of free IAA in tld1-D due to the conjugation of IAA with amino acids greatly facilitated the accumulation of late-embryogenesis abundant mRNA compared with the wild type. The direct regulation of such drought-inducible genes by changes in the concentration of IAA provides a model for changes in plant architecture via the process of drought adaptation, which occurs frequently in nature.