水稻籽粒数是一个对粮食产量有很大贡献的农艺性状。 在水稻(Oryza Sativa)中，OsMKKK10-OsMKK4-OsMPK6级联反应受双特异性磷酸酶GSN1负调控，协调籽粒数和籽粒大小之间的权衡。 然而，GSN1-MAPK模块上下游调节每穗粒数的具体成分仍然不清楚。
在这里，我们报道了ERECTA1(OsER1)，每穗粒数的负调控因子，作用于OsMKKK10-OsMKK4-OsMPK6级联的上游，并且OsER1-OsMKKK10-OsMKK4-OsMPK6途径是维持细胞分裂素稳态所必需的。
OsMPK6直接与锌指转录因子DST相互作用并磷酸化，增强其对细胞分裂素OXIDASE2(OsCKX2)的转录激活，表明OsER1-OsMKKK10-OsMKK4-OsMPK6途径通过调节细胞分裂素代谢而形成穗部形态。
此外，DST或OsCKX2的过表达挽救了oser1、osmkk10、osmkk4和osmpk6突变体的小穗数表型，表明DST-OsCKX2模块位于OsER1-OsMKKK10-OsMKK4-OsMPK6遗传通路的下游。
这些发现揭示了MAPK信号通路和细胞分裂素代谢之间的特定crosstalk，揭示了发育信号如何调节植物激素稳态来塑造花序。
Abstract:
Grain number is a flexible trait that strongly contributes to grain yield. In rice (Oryza sativa), the OsMKKK10-OsMKK4-OsMPK6cascade, which is negatively regulated by the dual-specificityphosphataseGSN1, coordinates the trade-off between grain number and grain size. However, the specific componentsupstreamanddownstreamof the GSN1-MAPK module that regulatespikeletnumber perpanicleremain obscure. Here, we report that ERECTA1 (OsER1), a negativeregulatorofspikeletnumber perpanicle, actsupstreamof the OsMKKK10-OsMKK4-OsMPK6cascadeand that the OsER1-OsMKKK10-OsMKK4-OsMPK6pathwayis required to maintaincytokininhomeostasis. OsMPK6 directly interacts with and phosphorylates thezincfingertranscriptionfactor DST to enhance its transcriptional activation ofCYTOKININOXIDASE2 (OsCKX2), indicating that the OsER1-OsMKKK10-OsMKK4-OsMPK6pathwayshapespaniclemorphologyby regulatingcytokininmetabolism. Furthermore, overexpression of either DST or OsCKX2 rescued thespikeletnumberphenotypeof the oser1, osmkkk10, osmkk4, and osmpk6 mutants, suggesting that the DST-OsCKX2 module genetically functionsdownstreamof the OsER1-OsMKKK10-OsMKK4-OsMPK6pathway. These findings reveal specificcrosstalkbetween a MAPKsignalingpathwayandcytokininmetabolism,sheddinglight on howdevelopmentalsignalsmodulatephytohormonehomeostasis to shape theinflorescence.
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