请你收集资料告诉我为什么小麦和水稻成熟期穗子形状不一样,其背后包含的生理机制有哪些

Erstellt am: 28. Juni 2025

Beantwortet mit Deep Research von Chat01

Frage

请你收集资料告诉我为什么小麦和水稻成熟期穗子形状不一样,其背后包含的生理机制有哪些

Antwort

为了更好地为你研究小麦和水稻穗子成熟期形状差异的原因,请问你希望研究内容聚焦在哪些方面?例如:

  1. 是否需要对比具体品种的穗型差异?
  2. 你希望重点了解遗传机制、激素调控、营养分配、还是形态建成等方面的生理机制?
  3. 是否有指定的数据来源或期刊(如《中国农业科学》、Nature Plants 等)?

请提供你希望重点了解的方向,这样我可以更有针对性地展开研究。

Frage

比较传统的小麦和水稻。涉及到穗子形态问题的遗传机制和生理机制等原因都介绍一下。数据不指定你寻找就好

Antwort

明白了。我将为你研究传统小麦和水稻在成熟期穗子形状差异的原因,重点包括穗型差异的遗传机制与生理机制,如激素调控、基因表达、营养分配等方面。 我整理好相关资料后会尽快反馈给你。

Forschung

✨ I’m examining the morphological differences between wheat spikes and rice panicles, focusing on genetic and physiological mechanisms. This involves identifying key genes, plant hormones, nutrient distribution, and transcriptional regulatory networks.

🔍 Searched for wheat, rice, genes, and hormones

✨ OK, let's see. The current search results aren't quite hitting the mark. It might be worth tweaking the search terms to find more relevant info.

🔍 Searched for wheat spike vs rice panicle gene differences

✨ I discovered a promising source, “Architecture of Wheat Inflorescence: Insights from Rice,” likely reviewing differences between wheat and rice inflorescence development.

🌐 Read sciencedirect.com

✨ Considering SciDirect's accessibility and exploring alternatives like "Cell Press" or an older article on Rice–wheat comparative genomics.

🌐 Read pmc.ncbi.nlm.nih.gov

✨ I’m observing the distinct architectural layouts of wheat and rice. Wheat features a single spikelet per node, while rice shows a branched panicle with primary and secondary branches.

🌐 Read more from pmc.ncbi.nlm.nih.gov

✨ I’m unpacking whether the article's specific wheat genes can provide a broad comparative view. Considering wheat inflorescence and rice panicle differences as an alternative.

🔍 Searched for wheat spike vs rice panicle morphology

🌐 Read sciencedirect.com

✨ I'm thinking through alternative methods by searching with article titles or specific keywords.

🔍 Searched for wheat spike panicle morphology differences

✨ I’m mapping out the morphological differences and key genes controlling wheat and rice ear shapes, focusing on inflorescence architecture and genetic regulation.

🔍 Searched for rice inflorescence genes vs wheat spike

✨ I'm thinking "Architectures of Wheat Inflorescence: Insights from Rice" is crucial. If it's behind a paywall, key phrases might work. Alternatively, check out "Genetic and molecular pathways controlling rice inflorescence."

🌐 Read pmc.ncbi.nlm.nih.gov

🌐 Read researchgate.net

✨ Applying rice gene and signaling research to wheat spike development for optimized growth.

🔍 Searched for rice inflorescence and wheat spike development control

✨ I’m mapping out the sections of a genetic comparison between rice and wheat, considering morphological differences, regulatory genes, hormone roles, nutrient distribution, and transcriptional networks.

🌐 Read zh.wikipedia.org

✨ OK, let me see. I’m checking the details in the search snippet by clicking on the first result. This ensures the information is accurate and reliable.

🌐 Read zh.m.wikipedia.org

✨ I'm gathering info on wheat ear type studies. This involves examining shape formation, physiological traits, and external influences.

🌐 Read zwzz.chinacrops.org

✨ I'm evaluating the possibility that the timing out issue is due to the site being blocked. This could explain the connectivity problem.

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✨ I’m piecing together the article from "作物杂志" (Crops Journal), noting it’s about wheat ear morphological development and physiological features, with a focus on wheat, likely excluding rice.

🔍 Searched for spike panicle genes

✨ It seems to be discussing a crucial gene for controlling grasses and their branching patterns.

🌐 Read ebiotrade.com

✨ : Exploring Chinese terms like "穗状花序 圆锥花序 基因调控 小麦 水稻" to find relevant articles.

🔍 Searched for wheat spike rice panicle genes

✨ OK, let me see. This result seems promising, likely exploring genetic regulation in rice panicle architecture.

🌐 Read chinbullbotany.com

✨ OK, let me see. I’m starting to think about accessing result [0] through an alternative approach, given the likely restriction on direct fetch due to the site's policies.

🔍 Searched for rice spike genetic regulation research progress

✨ Hmm, I’m thinking about how 360Doc’s user-collected content fits into the research on rice panicle formation and regulation. It might offer a summarized view worth noting.

🌐 Read 360doc.com

✨ I’m gathering info on rice panicle development and regulation, organizing findings into impactful sections.

🔍 Searched for rice large spike formation regulation research progress

✨ I'm looking into the specific anatomical differences between wheat and rice, particularly focusing on their inflorescence structures such as the wheat spike and rice panicle. This involves examining descriptions and references from various sources to ensure accuracy.

🔍 Searched for wheat unbranched spike vs rice branched panicle

✨ I'm digging into the FZP gene's key role in rice panicle architecture, focusing on its impact on lateral branches and spikelets, as detailed in the referenced lines.

🌐 Read nature.com

✨ I’m curious about genes like APO1, Gn1a, and IPA1/WFP, which impact spikelet and panicle structure in rice, and considering similar wheat genes for spike architecture.

🔍 Searched for WAPO1 wheat spikelet number gene

✨ Mapping the genetic control of spike architecture, focusing on WAPO1's F-box gene, and assessing hormonal impacts like gibberellin and cytokinin on inflorescence development.

🔍 Searched for gibberellin cytokinin inflorescence branching in rice and wheat

✨ I'm piecing together the idea that more gibberellic acid (GA) might boost inflorescence branching, potentially leading to increased yields.

🌐 Read academic.oup.com

✨ I'm working on how CK, auxin, and GA regulate rice inflorescence formation.

🔍 Searched for hormone regulation of inflorescence development

✨ OK, I’m pulling together how hormones shape spikelet development by examining gibberellins, cytokinins, and abscisic acid. This highlights natural growth patterns.

🔍 Searched for gibberellin spike differentiation development in rice and wheat

✨ I'm exploring a news article that might shed light on GA's mechanism in rice panicle regulation, possibly involving KNOX and its relationship with CK.

🌐 Read cemps.cas.cn

✨ I’m examining how GNP1, a GA20ox1 gene, boosts grain number by modulating cytokinin activity in panicle meristems, indicating a dynamic interaction between GA and cytokinin.

🔍 Searched for GA effect on rice and wheat panicle branching

✨ I’m thinking about collaborating with the PMC initiative. It seems like a promising step forward!

🌐 Read pmc.ncbi.nlm.nih.gov

✨ I'm moving through the document to line 779, which might have juicy info.

🌐 Read more from pmc.ncbi.nlm.nih.gov

✨ I’m looking at how gibberellin (GA) influences rice and wheat panicle architecture and yield, while cytokinins and abscisic acid (ABA) regulate meristem activity and stress responses.

🌐 Read sohu.com

✨ I’m mapping out wheat gene "wps1" and its link to paired spikelets. Interested in transcriptional factors like SPL, MADS domain genes, and meristem control factors.

🌐 Read news.bioon.com

✨ Identifying multiple regulators and a key module in wheat spike morphogenesis. Evaluating transcription factors and checking references for accuracy.

🌐 Read cas.cn

✨ I’m looking at the differences between wheat and rice inflorescences. Wheat has simple spikelets with one branching level, while rice features a more complex panicle with multiple branches and spikelets.

🌐 Read nature.com

✨ Combining snippets [25†L119-L128] and [3†L249-L257] for rice, and [38†L9-L16] and [26†L5-L13] for wheat, integrating gene effects and morphological traits.

🌐 Read pmc.ncbi.nlm.nih.gov

✨ I’m mapping out nutrient allocation in wheat and rice, focusing on spikelet degeneration from shading and carbon limits. This explores how nutritional status and N management influence grain set.

🌐 Read zwxb.chinacrops.org

✨ I’m working through different keyword combinations to find more relevant nutrient details. Progressing towards a clearer understanding.

🔍 Searched for spikelet development and nutrient allocation in wheat and rice

✨ I found that in wheat, a lower carbon to nitrogen ratio fosters spikelet formation, while a higher ratio later aids survival. Similar principles apply to rice, where nutrient coordination is crucial.

🔍 Searched for wheat spike rice panicle image

✨ It's worth noting that there's no direct image here. Images should be embedded if they are relevant to the main issue.

🔍 Searched for wheat rice spike image

✨ Piecing together morphological differences and gene control references, ensuring each claim is well-supported.

🌐 Read journals.plos.org

✨ ACKnowledging ABA's impact on spikelet survival and grain set, especially under stress. This ties into the detailed hormone and gene mechanisms highlighted earlier.

🔍 Searched for ABA spikelet development in wheat and rice

✨ Pulling together the context of ABA's effects on stress-induced floret abortion in developing spikes.

🌐 Read as-botanicalstudies.springeropen.com

✨ I'm thinking about how ABA influences spikelet abortion under stress, reducing yield in salt-treated wheat. Now, I'm looking into C/N ratio's role in spikelet initiation and survival.

🌐 Read nph.onlinelibrary.wiley.com

✨ I'm pulling together the details on how the SEP genes OsMADS5 and OsMADS34 work with RCN4 to curb inflorescence branching.

🔍 Searched for OsMADS5 OsMADS34 inflorescence branching

✨ I’m mapping out which citation to use, considering the snippet and its relevance to the context.

🌐 Read pmc.ncbi.nlm.nih.gov

✨ I’m gathering info on how increasing OsSPL14 expression boosts primary branches and spikelets yield. The guidelines suggest keeping paragraphs concise, around 3-5 sentences.

Research completed in 7m

Antwort

传统小麦与水稻穗型差异的遗传和生理机制比较

穗型的形态学差异

小麦成熟时的穗(即麦穗)为典型的穗状花序,穗轴上不分枝,每个节只着生一个无柄小穗 (Genes WHEAT FRIZZY PANICLE and SHAM RAMIFICATION 2 independently regulate differentiation of floral meristems in wheat - PMC) 。这些小穗沿穗轴交替排列,通常包含2–5朵可育的小花,最终形成麦粒 (Genes WHEAT FRIZZY PANICLE and SHAM RAMIFICATION 2 independently regulate differentiation of floral meristems in wheat - PMC) 。相较而言,水稻的穗称为圆锥花序(稻穗),表现出明显的分枝结构,即在中央穗轴上产生一级分枝,一级分枝基部的分生组织进一步形成二级分枝,其上着生小穗 (Identification of genomic regions controlling spikelet degeneration under FRIZZLE PANICLE (FZP) defect genetic background in rice | Scientific Reports) 。因此,水稻穗呈圆锥形展开,穗上含有主轴、一级和二级分枝以及众多小穗,通常分枝多、结构松散,而小麦穗则无长分枝、结构紧密 (Genes WHEAT FRIZZY PANICLE and SHAM RAMIFICATION 2 independently regulate differentiation of floral meristems in wheat - PMC) (Identification of genomic regions controlling spikelet degeneration under FRIZZLE PANICLE (FZP) defect genetic background in rice | Scientific Reports) 。小麦穗属于有限花序,有顶端小穗分化完成后穗轴生长停止(穗轴顶端常有终止小穗),而水稻圆锥花序趋于不定型生长,顶端分生组织在抽穗时可能仍持续分化小穗,使水稻穗可发育出更多的分枝和小穗 (Identification of genomic regions controlling spikelet degeneration under FRIZZLE PANICLE (FZP) defect genetic background in rice | Scientific Reports) 。

穗型发育的主要控制基因及调控机制

水稻: 水稻穗型由多个基因协同调控,其影响分枝数和小穗数的主效基因研究较为深入。经典基因例如 Gn1a(又称OsCKX2)是控制穗粒数的关键QTL,其功能缺失会降低穗分生组织中细胞分裂素氧化酶的活性,导致细胞分裂素(分蘖素)在幼穗分生组织中累积,显著增加每穗小穗数和穗粒数 (水稻穗型的遗传调控研究进展 - 植物学报) 。LAX1/LAX2 基因编码分生组织分裂相关因子,缺失会使水稻失去穗分枝;相应地,MOC1(MONOCULM 1)等上游调控因子正向调节LAX1,有助于分枝分生组织的形成 (Genetic control of branching patterns in grass inflorescences - PMC) (Genetic control of branching patterns in grass inflorescences - PMC) 。TAW1 (Tawawa1) 则通过提高花序分生组织活性、延缓其过早转变为小穗分生组织来增加分枝数,是水稻中特有的分生组织活性调控因子 (水稻穗型的遗传调控研究进展 - 植物学报) 。另外,IPA1(Ideal Plant Architecture1,即OsSPL14)编码SPL类转录因子,被证明可协调株型与穗型,其表达上调时能增加水稻穗的一级分枝数和穗粒数,从而提高产量 (Genetic control of branching patterns in grass inflorescences - PMC) 。DEP1(Dense Panicle 1)和APO1/APO2(Aberrant Panicle Organization 1/2)则影响穗轴分枝的长度和数量:例如,APO1编码F-box蛋白,突变会导致水稻穗分枝减少、穗型紧凑 (Identification of genomic regions controlling spikelet degeneration under FRIZZLE PANICLE (FZP) defect genetic background in rice | Scientific Reports) 。RFL(Rice FLORICAULA/LEAFY,同OsLFY)是水稻中的LEAFY同源基因,在小穗形成的阶段发挥作用,可促进小穗分生组织的产生并结束分枝分生组织阶段 (Identification of genomic regions controlling spikelet degeneration under FRIZZLE PANICLE (FZP) defect genetic background in rice | Scientific Reports) 。此外,FZP(FRIZZY PANICLE)基因编码AP2/ERF类转录因子,在分枝和小穗分化的平衡中起关键作用:正常情况下FZP促进小穗分化、抑制进一步的分枝产生;其功能缺失突变(frizzy panicle)会使水稻穗产生异常大量的二级、三级分枝,虽穗枝数大增但小穗大量退化 (Identification of genomic regions controlling spikelet degeneration under FRIZZLE PANICLE (FZP) defect genetic background in rice | Scientific Reports) 。因此,水稻穗型的遗传控制是多基因网络共同作用的结果,包括促进分枝的基因(如TAW1、SPL类)和限制分枝/促进小穗形成的基因(如FZP、OsMADS34等)共同调节穗型结构 (Identification of genomic regions controlling spikelet degeneration under FRIZZLE PANICLE (FZP) defect genetic background in rice | Scientific Reports) (Rice SEPALLATA genes OsMADS5 and OsMADS34 cooperate to ...) 。

小麦: 小麦穗为经进化简化的穗状花序,其分枝层级较少,每个节位通常只形成一个小穗。这一穗型由一系列基因严格控制,以确保只有一次分枝形成小穗 (遗传发育所等发现小麦增产的新基因----“中科院之声”电子杂志) 。研究发现,小麦的许多穗型调控基因与水稻对应基因存在同源关系。例如,WAPO1(Wheat Ortholog of APO1)即水稻APO1的同源基因,被鉴定为小麦7AL染色体上影响每穗小穗数的主效QTL基因。WAPO-A1的不同等位变异会导致穗上小穗数和籽粒数差异,通过突变和转基因实验证实WAPO1功能降低可增加每穗小穗数。WFZP(Wheat FRIZZY PANICLE)是小麦中的AP2/ERF类因子,与水稻FZP功能类似,正常等位基因确保每个穗节只产生一个小穗;突变或功能下降时,则出现超数小穗或穗分枝表型 (Genes WHEAT FRIZZY PANICLE and SHAM RAMIFICATION 2 independently regulate differentiation of floral meristems in wheat - PMC) 。例如,在普通小麦中敲除一个新发现的ERF类转录因子基因DUO-B1(该基因并未在以往育种中被利用),就导致穗节上长出复生小穗(paired spikelets)的突变体 (遗传发育所等发现小麦增产的新基因----“中科院之声”电子杂志) 。DUO-B1正常情况下上调分枝抑制因子WFZP的表达,限制小穗超生成;当DUO-B1突变失活时,WFZP表达降低,每个节位能分化出两个以上小穗,穗粒数显著增加 (遗传发育所等发现小麦增产的新基因----“中科院之声”电子杂志) 。这一突变体在田间表现为每穗小穗和粒数增加约10%,显示出增加穗分枝对提高小麦产量的潜力 (遗传发育所等发现小麦增产的新基因----“中科院之声”电子杂志) 。此外,小麦中还有一些调控穗形态的基因网络与开花时间和分蘖相关:例如TB1(Teosinte Branched1)和Ppd-1(光周期基因)通过调控开花基因FT和后续的VRN1表达,不仅影响开花期还关联穗分枝的形成 (科学家定位新的小麦穗发育调控基因_wps_Paired_研究) 。总的来说,小麦穗型主要由限制性分枝基因(如WFZP、DUO-B1)及决定小穗数目的基因(如WAPO1等)主导,它们的变异可导致穗型从单穗轴小穗增多到出现分枝穗的变化 (Genes WHEAT FRIZZY PANICLE and SHAM RAMIFICATION 2 independently regulate differentiation of floral meristems in wheat - PMC) (遗传发育所等发现小麦增产的新基因----“中科院之声”电子杂志) 。

植物激素对穗型发育的调控作用

穗的分化发育过程受到多种植物激素的影响,其中**赤霉素(GA)、细胞分裂素(CK)和脱落酸(ABA)**等发挥关键调控作用。

营养物质分配对穗子形态的影响

穗型的形成和最终穗粒数不仅取决于遗传和激素调控,也受到植物体内源库分配和营养供应状况的显著影响。小麦和水稻在穗发育过程中对光合产物和矿质营养的分配策略略有不同,导致穗型和结实特征上的差异。

在小麦中,营养物质(尤其碳水化合物与氮素)的供应平衡会影响小穗分化数目和存活率。有研究指出,小麦植株体内碳氮比(C/N)是决定穗分化和小穗存留的关键因素:在穗分化的早期,较低的C/N比(相对充足的氮素供应)有利于更多小穗原基的形成;而在随后的灌浆阶段,较高的C/N比(充足的碳水化合物供应)则有利于已分化小穗的存活和发育 (Super hybrid rice improved yield by increasing spikelet amount and ...) 。换言之,氮素充足有助于提高穗分生组织活性,使潜在小穗数增加,但若随后光合同化物(碳源)供应不足,这些额外的小穗和小花容易因竞争资源失败而退化。反之,后期碳源充裕(高C/N)能提高小穗的结实率,但如果前期氮素不足导致小穗分化数偏少,即使后期同化物充足,也难以显著提升穗粒数 (Super hybrid rice improved yield by increasing spikelet amount and ...) 。因此,高产的小麦穗通常依赖于前期适宜的氮素供应保证穗的大分化容量,以及中后期充足的光合产物确保更多小花结实灌浆。栽培上也常通过氮肥后移(追肥)和改善旗叶光合来调控这一平衡,以实现“大穗多粒”。

在水稻中,由于圆锥花序具有多级分枝结构,营养分配对穗型和结实的影响更为显著。要形成大穗,植株必须提供足够的营养支持众多的枝梗和小穗发育。研究表明,充足的养分(特别是氮素)供应以及碳水化合物同化能力,是水稻大穗形成的基础 (Spikelet differentiation and degeneration in rice varieties with ...) 。在水稻大穗品种中,常见现象是穗中上部的一次枝梗小穗所结籽粒(“强势粒”)饱满且先行灌浆,而穗基部二次枝梗上的小穗(“弱势粒”)因为发育稍晚且得不到同等的同化物供应,灌浆速率慢、结实率低 ([PDF] 植物激素对水稻籽粒灌浆、粒质量与品质的调控作用研究进展) 。这种穗内籽粒异质性正是营养分配影响穗型结果的体现:当源强(光合产物供给)不足或营养分配不均时,水稻穗下部的许多小穗会停滞不长,表现为颖花退化或空秕粒增加,穗子形态上呈现基部细弱、顶部粒密的特征 (Spikelet differentiation and degeneration in rice varieties with ...) 。相反,如果通过栽培措施(如增施肥、水分调控、延长功能叶寿命等)提高灌浆期的同化物供应并优化穗内营养分配,可减少弱势小穗的败育,提高全穗结实度,从而穗形更加丰满完整 (Suppressing spikelet degeneration increases grain yield under ...) 。在小麦中由于穗分枝层级少,穗内籽粒发育的差异相对较小,但同样存在顶部小花较弱、基部籽粒较大的趋势,只是程度弱于水稻。综合来看,良好的源库关系对于穗型的表型实现至关重要:营养分配充分均衡时,可充分表达遗传增产潜力,使小麦穗多成粒、水稻穗大而结实;反之,即使遗传上具备形成大穗的基础,若营养跟不上,也会出现小穗退化、穗型变小变瘦的结果 (Super hybrid rice improved yield by increasing spikelet amount and ...) (Spikelet differentiation and degeneration in rice varieties with ...) 。

穗型形成过程的转录调控网络研究进展

近年随着功能基因组学和多组学技术的发展,小麦和水稻穗发育的转录调控网络逐渐被解析,揭示出复杂的基因调控模块和信号网络共同塑造穗型。

小麦方面: 由于小麦基因组复杂、功能基因组研究起步相对较晚,穗发育关键因子的鉴定长期滞后。但最新研究通过多维组学和转录组调控网络分析取得突破。中国科学院肖军研究团队构建了小麦穗发育的动态转录组和表观图谱,搭建了穗发育过程的转录调控网络(TRN),系统鉴定出了大量潜在调控因子 (研究鉴定出小麦穗发育的转录调控因子 - 生物研究专区 - 生物谷) 。该研究覆盖小麦穗分化的8个关键时期,利用共表达分析和染色质可及性测序,预测并验证了一批调控穗发育的转录因子模块。其中,鉴定出227个潜在穗发育调控因子,有42个基因已经在小麦或水稻中被证明参与穗发育 (研究鉴定出小麦穗发育的转录调控因子 - 生物研究专区 - 生物谷) 。进一步功能筛选发现其中至少36个基因的突变会导致小麦开花时间或穗型的改变 (研究鉴定出小麦穗发育的转录调控因子 - 生物研究专区 - 生物谷) 。一个典型的例子是鉴定到的TaSPL15–TaAGLG1–TaFUL2调控模块:TaSPL15(一种SPL类转录因子)上调调控MADS-box基因TaAGLG1,进而影响另一MADS-box基因TaFUL2的表达,三者构成层级调控关系,在穗分化中发挥重要作用 (研究鉴定出小麦穗发育的转录调控因子 - 生物研究专区 - 生物谷) 。此外,还发现多个新的转录因子对穗型有显著影响。例如TaMYB30-A1是新鉴定的一个MYB家族转录因子,其突变能够改变穗长和小穗数 (研究鉴定出小麦穗发育的转录调控因子 - 生物研究专区 - 生物谷) 。研究揭示小麦穗发育关键因子WFZP(前述的小麦穗形态抑制因子)对TaMYB30-A1具有转录抑制作用;当TaMYB30-A1启动子区域存在特定自然变异时,该基因表达上调,可增加穗长、可育小穗数和穗粒数,在小麦驯化和现代育种中受到选择利用 (研究鉴定出小麦穗发育的转录调控因子 - 生物研究专区 - 生物谷) 。这些发现表明,小麦穗型形成受复杂的转录因子网络调控,不同转录因子之间存在层级调控和相互作用。例如,SPL、AP2/ERF、MADS、MYB、bHLH等多种转录因子各司其职,共同决定了穗分生组织的命运转换和小穗发育进程 (研究鉴定出小麦穗发育的转录调控因子 - 生物研究专区 - 生物谷) (研究鉴定出小麦穗发育的转录调控因子 - 生物研究专区 - 生物谷) 。建立在此基础上的小麦穗发育多组学数据库,将进一步加速关键基因的功能解析和分子设计育种应用。

水稻方面: 作为模式禾谷类作物,水稻穗发育的调控网络研究相对更完善,揭示出一系列重要的转录调控因子及其互作关系。在水稻穗的分枝转变为小穗的过程中,OsMADS34OsMADS5MADS-box转录因子起到关键节点作用。OsMADS34/OsMADS5(SEPALLATA类基因)被发现协同作用,通过抑制一类TFL1-样基因(如RCN4,即Rice CENTRORADIALIS 4)的表达来限制圆锥花序的过度分枝 (Rice SEPALLATA genes OsMADS5 and OsMADS34 cooperate to ...) 。当OsMADS34等功能减弱时,RCN类分生组织维持因子表达上升,导致花序分生组织维持期延长、分枝增多;反之,这些MADS因子的正常功能可确保花序及时转入小穗分化,避免无限制分枝 (Rice SEPALLATA genes OsMADS5 and OsMADS34 cooperate to ...) 。同时,水稻特有的分生组织身份转换调控因子也已被鉴定:如OsTFL1类基因(RCN1/RCN2等)决定穗顶端分生组织的命运,是控制花序确定性的关键,上述SEP类因子正是通过调控这些因子来实现对穗型的控制 (Rice SEPALLATA genes OsMADS5 and OsMADS34 cooperate to ...) 。在分枝形成早期,OsLFL(LEAFY同源物)和OsAP1(APETALA1同源物)等也参与决定分生组织是继续产生枝还是转化为小穗;这些基因与OsSPL、OsMADS等之间形成复杂的网络,共同影响穗分枝数量与小穗密度。

值得一提的是miR156–SPL–miR172通路在禾谷类穗分枝调控中的作用。水稻基因组中有多达19个OsSPL基因,其中多个受miR156调控 (Genetic control of branching patterns in grass inflorescences - PMC) 。在营养生长向生殖生长转换以及花序分枝过程中,miR156逐渐下降、SPL蛋白水平上升。这些SPL转录因子充当穗分生组织阶段转换的“开关”。例如,OsSPL14(IPA1)和OsSPL17表达上调能够促进穗的一次枝梗分生组织活动,提高分枝数和穗粒数 (Genetic control of branching patterns in grass inflorescences - PMC) ;相应地,过表达OsSPL14或降低miR156水平会加速分生组织由产生分枝转向产生小穗的过渡(即缩短分枝阶段),并提高FRIZZY PANICLE (FZP)等促小穗分化基因的表达 (Genetic control of branching patterns in grass inflorescences - PMC) 。另一例子,OsSPL9被报道可通过激活水稻RCN1(TFL1类基因)的表达,来延长圆锥花序分枝阶段,从而增加穗分枝和小穗数 (OsSPL转录因子调控水稻生长发育的研究进展) 。这些SPL因子还与下游的miR172-AP2类因子形成反馈调控环,细致地控制着花序发育的时间和分枝模式 (Genetic control of branching patterns in grass inflorescences - PMC) (Genetic control of branching patterns in grass inflorescences - PMC) 。因此,水稻穗型的转录调控网络呈现出多层级、动态平衡的特点:上游有miRNA与SPL的调控模块、中间有MADS-box和LEAFY类因子决定分生组织命运、下游有FZP这类AP2因子执行具体“小穗化”过程。这些因子之间既相互独立又紧密串联,确保水稻圆锥花序产生适宜数量的分枝和小穗。

总之,无论在小麦还是水稻中,穗型的形成都是基因调控网络与激素、营养信号交织作用的结果。传统小麦演化出单轴穗状花序,是多个抑制分枝基因长期选择的结果;而水稻保持了多级分枝的圆锥花序,其基因网络则着重于平衡“分枝数量与小穗分化”之间的关系。现代分子生物学研究正持续揭示更多穗型调控的关键因子(如小麦中的TaWUS、TaFT以及水稻中的OsMADS1等),并阐明它们组成的调控网络 (研究鉴定出小麦穗发育的转录调控因子 - 生物研究专区 - 生物谷) (Identification of genomic regions controlling spikelet degeneration under FRIZZLE PANICLE (FZP) defect genetic background in rice | Scientific Reports) 。这些研究进展不仅加深了我们对穗型差异遗传与生理基础的认识,也为培育理想穗型的高产作物提供了理论指导和基因资源支持。

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