楊莎,劉珂珂,劉穎,郭峰,王建國,高華鑫,孟靜靜,張佳蕾,萬書波
基于轉(zhuǎn)錄組分析花生單粒精播與多粒穴播植株莢果產(chǎn)量差異的分子機(jī)制
楊莎,劉珂珂,劉穎,郭峰,王建國,高華鑫,孟靜靜,張佳蕾,萬書波
山東省農(nóng)業(yè)科學(xué)院農(nóng)作物種質(zhì)資源研究所,濟(jì)南 250100
【目的】在中國,為保證出苗率及播種質(zhì)量,田間常采用多粒播種。然而,多粒穴播植株間的競爭往往限制了植株的生長和最終產(chǎn)量。為了解決這一矛盾,團(tuán)隊(duì)前期研究建立了單粒精準(zhǔn)播種的高產(chǎn)栽培技術(shù)。單粒精播技術(shù)的節(jié)種作用和增產(chǎn)效果結(jié)合起來能夠帶來更大的效益,實(shí)現(xiàn)節(jié)本增效。挖掘不同種植方式花生葉片、根系及莢果中的差異表達(dá)基因,探討單粒精播栽培技術(shù)提高花生莢果產(chǎn)量的分子機(jī)制,為進(jìn)一步推動(dòng)花生高產(chǎn)高效提供理論依據(jù)和技術(shù)支撐。【方法】以花生品種花育25號為試材,測定單粒精播和多粒穴播種植產(chǎn)量相關(guān)指標(biāo),分別取花生開花后30 d倒三葉和主根及側(cè)根、雞頭幼果期花生莢果進(jìn)行轉(zhuǎn)錄組測序,從分子水平闡述不同播種方式花生產(chǎn)量的差異?!窘Y(jié)果】與多粒穴播相比較,單粒精播種植方式下花生單株莢果數(shù)、單株飽果數(shù)、單株果重、經(jīng)濟(jì)系數(shù)均顯著提高。轉(zhuǎn)錄組數(shù)據(jù)組裝后,平均每庫包含4 430萬個(gè)讀數(shù)。通過不同比較組合中差異表達(dá)基因、GO和KEGG通路分析,與多粒穴播相比較,單粒精播種植植物葉片中參與赤霉素信號傳導(dǎo)、光信號傳導(dǎo)等過程的轉(zhuǎn)錄因子及光系統(tǒng)Ⅱ放氧復(fù)合體、葉綠體膜、氧化還原反應(yīng)等光合作用相關(guān)基因表達(dá)量升高;根系中生物脅迫和非生物脅迫誘導(dǎo)的苯丙素代謝途徑相關(guān)基因包括細(xì)胞色素P450基因、氧化還原基因、脅迫反應(yīng)轉(zhuǎn)錄因子和信號調(diào)節(jié)蛋白顯著富集。莢果發(fā)育初期淀粉和蔗糖代謝基因顯著富集,更加有利于花生莢果發(fā)育過程中籽仁充實(shí)?!窘Y(jié)論】花生葉片中光合相關(guān)基因表達(dá)上調(diào)能夠促進(jìn)光合效率提升,與產(chǎn)量的增加密切相關(guān);單粒精播提高了根系抗生物和非生物脅迫的能力,結(jié)合莢果發(fā)育初期能量物質(zhì)相關(guān)基因表達(dá)上調(diào)均有利于地下部花生莢果的發(fā)育,提高花生產(chǎn)量。
花生;單粒精播;產(chǎn)量;RNA-Seq;光合作用;苯丙素途徑
【研究意義】花生(L.)是世界范圍內(nèi)重要的油料作物和經(jīng)濟(jì)作物,每年貢獻(xiàn)全球產(chǎn)油量的20%及11%的蛋白供給,在農(nóng)民增收、農(nóng)業(yè)增效及緩解食用油供需矛盾等方面具有舉足輕重的地位[1-2]。在耕地緊張和糧油爭地矛盾日益突出的情況下,人們逐漸認(rèn)識到提高單產(chǎn)已成為花生增產(chǎn)的重要有效途徑。【前人研究進(jìn)展】生產(chǎn)中,為保證花生出苗率,人工播種習(xí)慣于一穴多粒,少的三粒,多的五六粒,不僅用種量高,一穴多株引起的株距減少及種植密度增大還會(huì)造成個(gè)體間競爭加劇,植株生長發(fā)育不一致,影響花生產(chǎn)量進(jìn)一步提高[3-4]。雖然目前播種機(jī)多是穴播兩粒,但因?yàn)榉N子大小不均,也經(jīng)常存在一穴多?,F(xiàn)象。團(tuán)隊(duì)針對傳統(tǒng)種植株間競爭排斥現(xiàn)象,提出“單粒精播、健壯個(gè)體、優(yōu)化群體”技術(shù)思路,創(chuàng)建出單粒精播高產(chǎn)栽培技術(shù),緩解株間競爭,節(jié)省種子20%,增產(chǎn)10%以上[4-5]。然而,單粒精播個(gè)體發(fā)育及提高花生產(chǎn)量的分子機(jī)制尚不清楚。近年來,主要圍繞單粒精播提高花生產(chǎn)量的生理機(jī)制展開系統(tǒng)研究,比較了單粒精播與雙粒穴播花生光合特性、冠層微環(huán)境[5]、生物學(xué)特性[6]、物質(zhì)代謝[7]、株間競爭效應(yīng)[8]、產(chǎn)量構(gòu)成[3]等方面的差異。【本研究切入點(diǎn)】傳統(tǒng)分子生物學(xué)方法研究該過程效率低,且難度大,隨著高通量測序技術(shù)的發(fā)展,轉(zhuǎn)錄組、蛋白質(zhì)組、代謝組等基因組分析方法越來越受到重視,通過這些技術(shù)的發(fā)展可以用來探索農(nóng)業(yè)生產(chǎn)中不同現(xiàn)象的分子機(jī)制,為解決科學(xué)問題提供了新的途徑?;ㄉ鷧⒖蓟蚪M的發(fā)表[9-11]促進(jìn)了人們對花生農(nóng)學(xué)重要現(xiàn)象和遺傳改良更好的理解?!緮M解決的關(guān)鍵問題】本研究主要通過轉(zhuǎn)錄組測序篩選單粒精播和多粒穴播的表達(dá)差異基因,揭示單粒精播栽培技術(shù)提高花生莢果產(chǎn)量的分子機(jī)制,為進(jìn)一步實(shí)現(xiàn)花生高產(chǎn)高效提供理論依據(jù)和技術(shù)支撐。
以花生品種花育25號(山東花生研究所提供)為材料,在山東省農(nóng)業(yè)科學(xué)院飲馬泉基地(36°43′N,117°5′E,中國濟(jì)南)進(jìn)行。土壤肥力狀況:有機(jī)質(zhì)含量為1.1%(W/W)、堿解氮82.7 mg·kg-1、有效磷36.2 mg·kg-1、有效鉀94.5 mg·kg-1、交換性鈣14.9 g·kg-1。播種前基施復(fù)合肥(N15P15K15)750 kg·hm-2、鈣鎂磷肥750 kg·hm-2,播種時(shí),用噻蟲咯霜靈拌種。其他管理措施同一般高產(chǎn)田。起壟種植,壟寬85 cm,壟長10 m,壟面寬50 cm,壟高10 cm,每壟種2行花生,行距25 cm,每種播種方式各種4壟。設(shè)單粒精播穴距10 cm,23.5萬穴/hm2,每穴1粒;三粒穴播穴距20 cm,11.8萬穴/hm2,每穴3粒;五粒穴播穴25 cm,9.4萬穴/hm2,每穴5粒(圖1)。開花后30 d,分別取倒三葉、主根和側(cè)根,分別命名為單粒葉(single seed leaf,SL)、三粒葉(three seeds leaf,TL)、五粒葉(five seeds leaf,F(xiàn)L)和單粒根(single seed root,SR)、三粒根(three seeds root,TR)、五粒根(five seeds root,F(xiàn)R),出現(xiàn)雞頭幼果期分別取果實(shí)單粒果(single seed pod,SP)、三粒果(three seeds pod,TP)、五粒果(five seeds pod,F(xiàn)P)用于轉(zhuǎn)錄組測序。采用3個(gè)生物學(xué)重復(fù)試驗(yàn),混合后的組織用于試驗(yàn)。
圖1 種植模式示意圖
花生生長至成熟期時(shí)選取10株植株,對其單株莢果數(shù)、單株飽果數(shù)、單株果重進(jìn)行測定。將莢果和植株干燥至定重,經(jīng)濟(jì)系數(shù)計(jì)算公式為:經(jīng)濟(jì)系數(shù)=莢果干重/(植株干重+莢果干重)。
用植物RNA提取試劑盒(Takara,Dalian,China)提取各樣品RNA。用Agilent 2100生物分析儀和Agilent RNA 6000 Nano試劑盒(Agilent,Santa Clara,CA,USA)檢測RNA的質(zhì)量和純度。篩選合格的RNA樣本,用寡聚(dT)法分離mRNA,并將其碎片化。然后合成第一鏈cDNA和第二鏈cDNA,構(gòu)建cDNA文庫。
使用Illumina NovaSeq 6000進(jìn)行雙端測序,通過CASAVA堿基識別將圖像數(shù)據(jù)轉(zhuǎn)化為序列數(shù)據(jù)。首先對fastq格式的原始數(shù)據(jù)進(jìn)行處理,過濾掉低質(zhì)量序列后得到高質(zhì)量數(shù)據(jù),用于后續(xù)分析。試驗(yàn)原始數(shù)據(jù)已提交至NCBI(BioProject:PRJNA944737)。使用Hisat2(v2.0.5)將高質(zhì)量序列與Tifrunner[11]的參考基因組進(jìn)行匹配。根據(jù)CUI等[12]方法對DEG(差異表達(dá)基因)、GO(基因本體)和KEGG進(jìn)行分析。通過TBtools實(shí)現(xiàn)基因表達(dá)的可視化[13]。在50%的樣本中選擇FPKM>5的基因進(jìn)行加權(quán)基因共表達(dá)網(wǎng)絡(luò)分析(weighted gene co-expression network analysis,WGCNA),方法參照文獻(xiàn)[14]。
選擇FPKM>5的基因進(jìn)行加權(quán)基因共表達(dá)網(wǎng)絡(luò)分析(WGCNA)。此外,由于低表達(dá)或無變化基因通常代表噪聲,因此,采用絕對中位差(median absolute deviation,MAD)對基因進(jìn)行篩選。采用軟閾值功率26,最小模塊大小為60,合并模塊閾值為0.30進(jìn)行模塊構(gòu)建,將模塊中的基因根據(jù)KEGG分類。
使用Prime Script RT Reagent Kit合成所取樣品中的cDNA。由Primer3(https://bioinfo.ut.ee/primer3/)設(shè)計(jì)基因特異性引物,3次試驗(yàn)重復(fù)。反應(yīng)條件為95 ℃ 5 min;95 ℃ 30 s,40個(gè)循環(huán);60 ℃ 30 s。以花生為內(nèi)參基因。采用2?△△CT法進(jìn)行相對定量分析[15]。采用SPSS 26.0軟件進(jìn)行顯著性分析。
單株莢果數(shù)和莢果重是影響花生產(chǎn)量的直接因素。單粒精播處理的單株莢果數(shù)、單株飽果數(shù)和單株果重均高于三粒及五粒穴播,每穴產(chǎn)量:單粒精播<三粒穴播<五粒穴播;理論總產(chǎn)量:單粒精播>三粒穴播>五粒穴播(表1)。
利用Illumina 2000對不同播種方式的花生幼苗進(jìn)行轉(zhuǎn)錄組測序,構(gòu)建了27個(gè)轉(zhuǎn)錄組文庫(每個(gè)處理有3個(gè)文庫重復(fù))。經(jīng)過原始數(shù)據(jù)過濾、測序錯(cuò)誤率檢查、GC含量分布檢查,獲得了179.44 Gb的clean data。每個(gè)樣品的clean data達(dá)到7.47 Gb,Q30百分比平均為92.90%(表2)。表明高通量測序數(shù)據(jù)是高度可靠的。
表1 不同種植方式下花生成熟期單株莢果的變化
不同小寫字母表示處理間差異顯著(<0.05)。下同 Different small letters meant significant difference at<0.05 level. The same as below
表2 轉(zhuǎn)錄組測序基礎(chǔ)數(shù)據(jù)統(tǒng)計(jì)分析
SL:單粒葉;TL:三粒葉;FL:五粒葉;SR:單粒根;TR:三粒根;FR:五粒根;SP:單粒果;TP:三粒果;FP:五粒果。下同
SL: single seed leaf; TL: three seeds leaf; FL: five seeds leaf; SR: single seed root; TR: three seeds root; FR: five seeds root; SP: single seed pod; TP: three seeds pod; FP: five seeds pod. The same as below
在測序樣本中,根據(jù)差異表達(dá)水平分析差異表達(dá)基因(DEGs)。對所鑒定的基因進(jìn)行功能注釋和富集分析。SL vs TL、SL vs FL、TL vs FL 3對比較組中表達(dá)差異基因數(shù)分別為599、489和337(圖2)。進(jìn)一步對這些差異基因進(jìn)行GO分類,分別為生物進(jìn)程、分子功能和細(xì)胞組分3個(gè)部分。結(jié)果表明,上調(diào)DEGs主要富集在光系統(tǒng)Ⅱ放氧復(fù)合體(photosystem Ⅱ oxygen evolving complex)、類囊體膜(thylakoid membrane)、氧化還原酶復(fù)合體(oxidoreductase complex)及光系統(tǒng)Ⅱ(photosystem Ⅱ);下調(diào)DEGs主要富集在核小體組裝(nucleosome assembly)、染色質(zhì)組裝(chromatin assembly)、核小體組織(nucleosome organization)、DNA包裝(DNA packaging)(表3)。SL vs FL組中,上調(diào)基因KEGG通路主要富集在植物-病原體互作(plant-pathogen interaction)、甘油脂代謝(glycerolipid metabolism)、類胡蘿卜素合成(carotenoid biosynthesis)等,下調(diào)基因KEGG通路主要富集在硫胺素代謝(thiamine metabolism)和2-氧代羧酸代謝(2-Oxocarboxylic acid metabolism)。SL vs TL組中,上調(diào)基因的KEGG通路主要富集在甘油脂代謝(glycerolipid metabolism)、卟啉和葉綠素代謝途徑(porphyrin and chlorophyll metabolism),而下調(diào)基因的KEGG通路主要富集在不同氨基酸代謝途徑(arginine and proline metabolism; Cysteine and methionine metabolism)(表3)。轉(zhuǎn)錄因子(如MYB、GRAS和WRKY家族)基因在SL vs TL、SL vs FL組中均上調(diào)表達(dá)。熱激蛋白Hsp70及分子伴侶DnaJ的表達(dá)量也顯著增加,有助于增加光合膜的穩(wěn)定性(表4)。
當(dāng)單粒精播種植模式變?yōu)橐谎ㄈ;蛭辶7N植時(shí),花生根系的生長發(fā)育過程隨之發(fā)生變化。SR vs TR、SR vs FR、TR vs FR 3對比較組中表達(dá)差異基因數(shù)分別為2 024、2 220和1 246(圖2)。與三粒及五粒播種種植模式相比較,單粒精播上調(diào)基因GO富集主要包括過氧化物酶活性(peroxidase activity)、氧化還原酶活性(oxidoreductase activity)及對氧化脅迫的響應(yīng)(response to oxidative stress);下調(diào)基因同樣主要富集在糖脂轉(zhuǎn)運(yùn)蛋白活性(glycolipid transporter activity)及磺基轉(zhuǎn)移酶活性(sulfotransferase activity)、二糖及低聚糖的生物合成途徑(oligosaccharide biosynthetic process)。KEGG通路富集顯示,與一穴五粒種植相比較,單粒精播花生根系中上調(diào)基因富集在苯丙素生物合成(phenylpropanoid biosynthesis)、MAPK信號途徑(MAPK signaling pathway)、植物-病原體互作(plant-pathogen interaction),下調(diào)基因主要富集在淀粉和蔗糖代謝(starch and sucrose metabolism)。與一穴三粒種植相比較,單粒精播花生根系中上調(diào)基因富集在植物-病原體互作(plant- pathogen interaction)、苯丙素合成(phenylpropanoid biosynthesis)、MAPK信號途徑(MAPK signaling pathway)及類黃酮生物合成(flavonoid biosynthesis);下調(diào)基因主要富集在剪接體(spliceosome)、嘌呤代謝(purine metabolism)等途徑(表3)。相應(yīng)地,MAPK信號途徑中聚酮環(huán)化酶(polyketide cyclase)、氨基轉(zhuǎn)移酶Ⅰ類和Ⅱ類(aminotransferase classⅠandⅡ)、蛋白激酶(protein kinase domain)等差異表達(dá)基因在單粒精播根中表達(dá)上調(diào)(表4)。
圖2 不同播種方式下花生葉片、根系及莢果差異表達(dá)基因統(tǒng)計(jì)(A)和韋恩圖(B)
表3 不同播種方式下花生葉片、根及莢果中差異表達(dá)基因GO和KEGG富集分析
表4 單粒精播種植葉片、根及莢果中與產(chǎn)量相關(guān)差異表達(dá)基因列表
SP vs TP、SP vs FP、TP vs FP 3對比較組中表達(dá)差異基因數(shù)分別為5 137、918和1 467(圖2)。SP vs TP中花生莢果上調(diào)基因GO富集在多糖代謝過程(polysaccharide metabolic process)、對生物刺激的反應(yīng)(response to biotic stimulus)及多聚半乳糖醛酸酶活性(polygalacturonase activity);下調(diào)基因GO富集在DNA復(fù)制、代謝及組裝過程(DNA replication、DNA metabolic process、Chromosome、DNA packaging complex)。SP vs FP單粒精播的花生莢果中GO富集主要包括多聚半乳糖醛酸酶活性(polygalacturonase activity)和內(nèi)肽酶活性(endopeptidase activity);下調(diào)基因GO富集包括金屬離子轉(zhuǎn)運(yùn)(metal ion transport)、質(zhì)外體(apoplast)及序列特異性DNA結(jié)合(sequence- specific DNA binding)(表3);相應(yīng)地,葉綠體(chloroplast)、生長素相關(guān)基因(response to auxin)和大量的泛素相關(guān)基因(ubiquitin-protein transferase activity、ubiquitin-like protein transferase activity)表達(dá)發(fā)生變化(表5)。KEGG通路富集顯示,與一穴三粒種植相比較,單粒精播的花生莢果中上調(diào)基因主要富集在苯丙素生物合成(phenylpropanoid biosynthesis)、生長素響應(yīng)(auxin response)及淀粉和蔗糖代謝(starch and sucrose metabolism);下調(diào)基因富集在DNA復(fù)制、錯(cuò)配修復(fù)(DNA replication、mismatch repair)和糖酵解/糖異生(glycolysis/ gluconeogenesis);與一穴五粒種植相比較,單粒精播的花生莢果中上調(diào)基因主要富集在苯丙素生物合成(phenylpropanoid biosynthesis)及淀粉和蔗糖代謝(starch and sucrose metabolism),下調(diào)基因主要富集在植物-病原體互作(plant-pathogen interaction)和脂肪酸降解(fatty acid degradation)(表3)。
花生的根和果均為地下部生長,因此,光照對其生長發(fā)育過程不能產(chǎn)生直接影響。與單粒播種相比較,SR vs FR(2 220 DEGs)和SR vs TR(2 024 DEGs)中的相同的DEGs數(shù)僅為602個(gè),而大部分DEGs為SR vs FR和SR vs TR中特異表達(dá)的,很可能是由于增加種植密度后造成的。有趣的是,這602個(gè)DEGs的GO和KEGG富集項(xiàng)主要與不同物質(zhì)如苯丙素、黃酮類合成途徑及氨基酸等代謝途徑相關(guān)(圖3-A)。表明多粒種植均會(huì)引起株間競爭,調(diào)節(jié)植物生長發(fā)育及代謝功能的相關(guān)物質(zhì)合成途徑關(guān)鍵基因表達(dá)發(fā)生顯著變化。相應(yīng)地,增加種植密度后SP vs FP(9 180 DEGs)和SP vs TP(5 137 DEGs)中共有DEGs數(shù)為400,這400個(gè)DEGs的GO項(xiàng)主要富集在葡聚糖代謝途徑,GO條目中數(shù)量富集最多的為碳水化合物代謝途徑;KEGG途徑則主要富集在MAPK信號途徑(圖3-B)。
加權(quán)基因共表達(dá)網(wǎng)絡(luò)分析(WGCNA)用于挖掘組織特異性模塊和與表型相關(guān)的關(guān)鍵基因。為了探索不同播種方式下發(fā)揮重要作用的關(guān)鍵基因和共表達(dá)網(wǎng)絡(luò),通過WGCNA分析了樣品中的10 299個(gè)DEGs。為了構(gòu)建無標(biāo)度網(wǎng)絡(luò),將最優(yōu)軟閾值設(shè)置為11。通過使用函數(shù)鄰接和tom相似性建立鄰接矩陣和tom重疊矩陣。根據(jù)動(dòng)態(tài)切割劃分模塊,總共獲得了16個(gè)模塊,使用標(biāo)記熱圖函數(shù)來可視化和分析模塊與樣品之間的關(guān)系。相關(guān)系數(shù)大于0.65且<0.05的模塊被定義為樣本特異性模塊,因此,在6個(gè)樣本中獲得了25個(gè)組織特異性模塊(圖4-A)。棕褐色與SR呈正相關(guān);藍(lán)綠色和淺青色與TR呈正相關(guān);黃綠色和品紅色分別與FR和SP呈正相關(guān)。TP和FP的特定模塊分別為藍(lán)綠色和紅色。
表5 SP vs TP中DEGs的GO條目
A:SR vs FR,SR vs TR;B:SP vs FP,SP vs TP
為了深入了解不同種植方式的代謝途徑,對上述特定模塊上的基因進(jìn)行了KEGG富集分析。結(jié)果表明,SR中三羧酸循環(huán)途徑豐富富集;在TR中,有機(jī)含硒化合物代謝途徑及鞘糖脂生物合成途徑富集;而花生四烯酸代謝途徑在FR中富集(圖4-B)。SP特異性模塊基因在剪接體、真核生物中的核糖體生物發(fā)生和肌醇磷酸代謝等途徑中富集;TP特異性模塊基因也在DNA復(fù)制、生物素代謝、錯(cuò)配修復(fù)和核苷酸切除修復(fù)等途徑中富集;FP特異性模塊基因在咖啡因代謝、剪接體和酮體的合成與降解等途徑中富集(圖4-B)。
與單粒精播相比較,三粒穴播和五粒穴播下調(diào)的差異表達(dá)基因均在苯丙烷類生物合成富集。苯丙烷類物質(zhì)是一類植物的次生代謝產(chǎn)物,在植物發(fā)育中起著至關(guān)重要的作用。因此,進(jìn)一步篩選了苯丙烷類物質(zhì)在不同播種方式調(diào)節(jié)下根及果中相關(guān)基因的表達(dá)情況。
圖4 加權(quán)基因共表達(dá)網(wǎng)絡(luò)分析
當(dāng)單粒精播種植模式變?yōu)橐谎ㄈ;蛭辶r(shí),下調(diào)的苯丙烷類物質(zhì)相關(guān)基因主要包括過氧化物酶、糖基水解酶和細(xì)胞色素P450(圖5)。根中苯丙烷類物質(zhì)中有12個(gè)過氧化物酶基因在密度增加后表達(dá)量降低,相應(yīng)地,莢果中有9個(gè)過氧化物酶基因在密度增加后表達(dá)量降低。共有7個(gè)糖基水解酶基因被上調(diào),糖基水解酶具有調(diào)控植物生長發(fā)育和脅迫應(yīng)答的作用。
圖5 花生根及莢果中苯丙烷類途徑相關(guān)基因表達(dá)分析
為驗(yàn)證轉(zhuǎn)錄組測序結(jié)果中基因表達(dá)量的準(zhǔn)確性,隨機(jī)挑選了15個(gè)基因進(jìn)行不同處理下的qRT-PCR驗(yàn)證。將qRT-PCR結(jié)果與轉(zhuǎn)錄組測序數(shù)據(jù)比對發(fā)現(xiàn),15個(gè)差異表達(dá)基因與轉(zhuǎn)錄組數(shù)據(jù)基本一致(圖6),同時(shí)RNA-seq數(shù)據(jù)與qRT-PCR結(jié)果在0.01水平上線性關(guān)系良好,2達(dá)到0.9506(圖6),表明轉(zhuǎn)錄組測序數(shù)據(jù)的可靠性,可以用來分析不同播種方式條件下花生葉片、根及莢果中的差異表達(dá)基因。
不同生物和非生物脅迫嚴(yán)重影響全球作物產(chǎn)量和糧食安全[16]。旱、澇、酸化、鹽堿等非生物逆境和傳統(tǒng)穴播兩?;蚨嗔7N植引起的生物逆境,成為制約花生單產(chǎn)突破的瓶頸[17]。近年來,隨著測序技術(shù)的發(fā)展,基因組和轉(zhuǎn)錄組廣泛應(yīng)用于農(nóng)業(yè)生產(chǎn)問題的研究。通過轉(zhuǎn)錄組深度挖掘花生單粒精播與多粒穴播種植的關(guān)鍵差異基因,全面解析單粒精播增產(chǎn)的分子新機(jī)制,為解析花生栽培高產(chǎn)提供有效工具。
作物產(chǎn)量的形成實(shí)質(zhì)是源庫流協(xié)調(diào)作用的結(jié)果。非生物脅迫通過氣孔(氣孔關(guān)閉)或非氣孔(如光系統(tǒng)被破壞和光合作用關(guān)鍵酶活性降低)降低光合作用,導(dǎo)致源強(qiáng)度降低[18-19],從而減少同化物向籽粒中的轉(zhuǎn)運(yùn)分配,降低產(chǎn)量。在本研究中,單粒精播種植葉片中MYB及WRKY等轉(zhuǎn)錄因子家族較一穴三粒和五粒播種表達(dá)量增加,這些轉(zhuǎn)錄因子在非生物逆境響應(yīng)過程中發(fā)揮重要作用[20-21]。此外,一些參與赤霉素信號傳導(dǎo)、光信號傳導(dǎo)等過程的轉(zhuǎn)錄因子如HSP70、DnaJ和GRAS,在單粒精播種植葉片中表達(dá)量上升(表4)。DnaJ蛋白作為分子伴侶,在調(diào)節(jié)生物體的生長發(fā)育和適應(yīng)環(huán)境中起著關(guān)鍵作用[22]。一穴三粒及五粒種植更加加劇了花生葉片對光源的競爭,植株間生長空間不足,受光面積減少。單粒精播葉片中光系統(tǒng)Ⅱ放氧復(fù)合體、葉綠體膜、氧化還原反應(yīng)等相關(guān)基因表達(dá)上調(diào),有助于提高光合效率(表3)。光合作用為農(nóng)作物產(chǎn)量的形成提供了主要的物質(zhì)基礎(chǔ),因此,單粒精播能夠促進(jìn)花生建立強(qiáng)大的群體質(zhì)量體系,形成“強(qiáng)源”,為干物質(zhì)的積累提供基礎(chǔ)條件。
根系組織的生長發(fā)育對花生的產(chǎn)量尤為重要,健壯的根系是作物生長和高產(chǎn)的基礎(chǔ)[23]。病蟲害等生物脅迫和鹽堿、漬澇、機(jī)械損傷、干旱等非生物脅迫嚴(yán)重影響花生的生長發(fā)育。在本研究中,與三粒及五粒種植相比,單粒精播根系中氧化還原及抗氧化活性物質(zhì)、苯丙素途徑及MAPK信號途徑等GO和KEGG富集上調(diào)(表3),相應(yīng)地,苯丙素途徑相關(guān)基因(過氧化物酶基因、半胱氨酸分泌蛋白家族和細(xì)胞色素P450)表達(dá)上調(diào)(圖5)。在擬南芥中,過氧化物酶參與脅迫耐性,并具有清除活性氧(ROS)和阻止DNA損傷的作用[24]。過氧化物酶負(fù)調(diào)節(jié)ABA介導(dǎo)地抑制種子萌發(fā)[25],同時(shí)在激素介導(dǎo)調(diào)節(jié)側(cè)根發(fā)育中起重要作用[26]。苯丙素是目前研究較多的植物次生代謝類物質(zhì),包括類黃酮、花青素、單木質(zhì)素和單寧。類黃酮由苯丙氨酸通過苯丙素途徑合成,而苯丙氨酸則通過莽草酯途徑合成。一般苯丙素途徑的第二步涉及C4H的活性,C4H是植物中的一種細(xì)胞色素P450單加氧酶,催化反式肉桂酸的羥基化生成對香豆酸。這也是類黃酮合成途徑中的第一個(gè)氧化反應(yīng)[27]。在白楊和擬南芥中,C4H的表達(dá)水平與重要的苯丙素類代謝產(chǎn)物木質(zhì)素的含量有關(guān)。這些苯丙素類物質(zhì)能夠通過參與調(diào)控光合作用、營養(yǎng)吸收、調(diào)節(jié)生長、細(xì)胞分裂、維持氧化還原穩(wěn)態(tài)等過程提高植物對生物或非生物逆境的抗性和穩(wěn)定性[28]。非生物逆境下,苯丙素生物合成途徑受到刺激,產(chǎn)生多種具有較強(qiáng)抗氧化潛能的酚類化合物[29]。酚類化合物主要通過清除鹽脅迫下植物體內(nèi)有害的ROS提高植物耐受性[30-31]。參與MAPK級聯(lián)的基因包括互聯(lián)的MAPK、MAPKK和MAPKKK,這些級聯(lián)在植物激素、生物脅迫和非生物脅迫的信號轉(zhuǎn)導(dǎo)中同樣發(fā)揮重要作用[32]。這些苯丙素類物質(zhì)及MAPK級聯(lián)途徑在單粒精播種植的花生根系中富集(表3),協(xié)助花生提高根系的抗病及抗氧化能力,從而保障花生的優(yōu)質(zhì)高產(chǎn)。
糖分作為光合產(chǎn)物以蔗糖的形式輸入籽粒,隨后經(jīng)過4種關(guān)鍵酶的催化作用轉(zhuǎn)化為淀粉。淀粉主要在胚乳細(xì)胞中儲(chǔ)藏,處于不斷被貯存同時(shí)不斷被利用的狀態(tài),對果實(shí)發(fā)育起著物質(zhì)和能量供應(yīng)的重要作用。儲(chǔ)藏物質(zhì)一旦無法積累,就會(huì)引起種子敗育[33]。單粒精播種植莢果中淀粉和蔗糖代謝基因富集有利于花生莢果發(fā)育過程中籽仁充實(shí),產(chǎn)量增加(表1和表3)。此外,在DEGs中還發(fā)現(xiàn)了大量的葉綠體、生長素相關(guān)基因和大量的泛素化蛋白(表5)。因此,推測有2條信號轉(zhuǎn)導(dǎo)途徑參與單粒精播花生莢果的發(fā)育。一種是從葉綠體及光合作用開始通過泛素化參與調(diào)控細(xì)胞周期、果實(shí)發(fā)育等過程;二是通過生物和非生物脅迫的信號調(diào)控及物質(zhì)代謝向下游傳遞信號。
多粒穴播的株間競爭往往限制了植株的生長和最終產(chǎn)量。通過轉(zhuǎn)錄組測序發(fā)現(xiàn),該過程涉及光合作用相關(guān)基因表達(dá)量變化,苯丙素代謝途徑相關(guān)基因表達(dá)發(fā)生變化,包括細(xì)胞色素P450基因、氧化還原基因、脅迫反應(yīng)轉(zhuǎn)錄因子等。此外,蛋白淀粉和蔗糖代謝基因顯著富集,這些通路中基因表達(dá)量的改變有助于花生地上部植株生長及地下部莢果發(fā)育過程,提高花生產(chǎn)量。
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The Molecular Mechanism of Pod Yield Difference between Single- Seeding Precision Sowing and multi-seeds sowing of Peanut Based on Transcriptome Analysis
YANG Sha, LIU KeKe, LIU Ying, GUO Feng, WANG JianGuo, GAO HuaXin, MENG JingJing, ZHANG JiaLei, WAN ShuBo
Institute of Crop Germplasm Resources, Shandong Academy of Agricultural Sciences, Jinan 250100
【Objective】In China, in order to ensure the emergence rate and quality of seedlings, the field often adopts multiple seed seeding. However, inter-plant competition in multi-seeds sowing often limits the growth and eventual yield of subsequent plants. In order to solve this contradiction, the team studied and established the high-yield cultivation technology of single-seed precision seeding. The combination of seed saving and yield increase effect of single-seed precision seeding technology can bring greater benefits and realize cost savings and increased efficiency. the differentially expressed genes in peanut leaves, roots and pods under different planting methods were used to explore the regulatory mechanism of single-seeding precision sowing to improve peanut pod yield, providing theoretical basis and technical support for further promoting peanut high yield and high efficiency. 【Method】Peanut variety Huayu 25 was used as the test material, while the yield related indexes of single-seed sowing and multi-seeds sowing were determined. Inverted three leaves, taproot and lateral root of peanut at 30 days after flowering and peanut pod at young fruit stage of chicken head were selected for transcriptome sequencing, and the yield differences of peanut under different sowing methods were revealed on the molecular level. 【Result】Compared with multi-seeds sowing, the pod number per plant, full fruit number per plant, fruit weight per plant and economic coefficient of single-seed sowing were significantly increased. After the transcriptome data is assembled, each library contains an average of 44.3 million readings. Through the analysis of differentially expressed genes, GO and KEGG pathways in different combinations, it was found that the expression levels of transcription factors, photosystem Ⅱ oxygen-releasing complex, chloroplast membrane, oxidation-reduction reaction and other genes involved in the processes of GA signal and light signal transduction were increased in the leaves of plants under single-seed sowing compared with multi-grain cave seeding. Genes related to phenylpropyl metabolism pathway induced by biological and abiotic stress were significantly enriched in roots, including cytochrome P450 gene, oxidation-reduction gene, stress response transcription factor and signal regulatory protein. The accumulation of starch and sucrose metabolism genes was more conducive to seed kernel enrichment during pod development. 【Conclusion】The up-regulated expression of photosynthetic related genes in peanut leaves at seedling stage could promote the increase of photosynthetic efficiency, which was closely related to the increase of yield. Single-seed sowing improved the ability of root system to resist biological and abiotic stress, and combined with the up-regulation of energy and material related genes in the early stage of pod development, it was beneficial for the development of underground peanut pod and increased peanut yield.
peanut; single seed precision sowing; yield; RNA-Seq; photosynthesis; phenylpropanoid pathway
10.3864/j.issn.0578-1752.2023.22.003
2023-04-30;
2023-06-25
國家重點(diǎn)研發(fā)計(jì)劃(2022YFD1000105-2)、泰山學(xué)者工程、山東省重點(diǎn)研發(fā)計(jì)劃(2021LZGC026,2022CXPT031)、山東省農(nóng)業(yè)科學(xué)院農(nóng)業(yè)科技創(chuàng)新工程(CXGC2023A20)
楊莎,E-mail:yangsha0904@126.com。通信作者張佳蕾,E-mail:zhangjialei19@163.com。通信作者萬書波,E-mail:wanshubo2016@163.com
(責(zé)任編輯 李莉)