柑橘CsMEKK1-1响应黄龙病菌侵染的表达特征与功能探究

doi:10.16420/j.issn.0513-353x.2023-0792

摘要/Abstract

摘要：

丝裂原活化蛋白激酶（mitogen-activated protein kinase，MAPK）信号通路在柑橘应答黄龙病（Huanglongbing，HLB）危害中起关键作用，但其响应的关键基因及机制有待阐明。对受黄龙病病原菌韧皮部杆菌亚洲种“Candidatus Liberibacter asiaticus”（CLas）侵染4个月的‘锦橙’（Citrus sinensis‘Jincheng’）叶肉和主脉进行转录组测序分析，发现差异表达基因显著富集在MAPK信号通路，参与MAPK信号通路第一级联反应的4个MEKK1基因在感病叶肉中上调表达，在主脉中无差异表达。实时荧光定量PCR（RT-qPCR）分析表明，4个CsMEKK1在易感HLB‘锦橙’和耐病‘马蜂柑’的不同组织中受CLas诱导的表达差异明显。选取差异表达水平最显著的CsMEKK1-1深入研究。生物信息分析结果表明CsMEKK1-1符合MEKK亚家族的特征。烟草亚细胞定位显示，CsMEKK1-1主要位于细胞质、细胞核和叶绿体。以‘锦橙’叶片为试材，qRT-PCR分析显示CsMEKK1-1具有响应水杨酸（SA）、茉莉酸（JA）、乙烯（ETH）、脱落酸（ABA）和CLas鞭毛小肽CLas-flg22诱导的表达特征，并且响应SA、JA、ETH诱导下调表达，CLas-flg22主要下调CsMEKK1-1表达。构建CsMEKK1-1的过表达和RNAi干扰载体，利用发根农杆菌转化受CLas感染的‘锦橙’枝条，再生转基因毛状根，定量PCR分析发现，CsMEKK1-1正调控毛状根中CLas的增殖，预示CsMEKK1-1可能是一个黄龙病感病基因。

关键词: 柑橘, 黄龙病, MAPK信号通路, CsMEKK1-1, 感病基因

Abstract:

It has been shown that MAPK（mitogen-activated protein kinase）signaling pathway plays a key role in regulating citrus Huanglongbing（HLB）disease，but the key genes and mechanisms involved in this pathway need to be elucidated. Comparative transcriptome analysis of the mesophyll and midrib tissues from‘Jincheng’oranges[Citrus sinensis (L.) Osbeck]at the early stage（four months）of“CandidatusLiberibacter asiaticus”（CLas）infection revealed that differentially expressed genes（DEGs） were significantly enriched in the MAPK signaling pathway. Among these DEGs，four MEKK1 genes involved in the first cascade of the MAPK signaling pathway were up-regulated in the mesophylls，but they had no differential expression in midribs. Real-time fluorescence quantitative PCR（qRT-PCR）analysis showed that the expression of four CsMEKK1 genes were significantly different in different tissues from the HLB-susceptible‘Jincheng’orange and the HLB-tolerant‘Mafenggan’orange（Citrus hystrix）during CLas infection. CsMEKK1-1 showing the most significantly differential expression was selected for further analysis. Bioinformatics analysis showed that CsMEKK1-1 belongs to the MEKK gene family. Tobacco subcellular localization showed that CsMEKK1-1 was localized in the cell cytoplasm，nucleus and chloroplast. Expression characteristics of CsMEKK1-1 gene in response to salicylic acid（SA），jasmonic acid（JA），abscisic acid（ABA），ethylene（ETH）and CLas-flg22 in healthy‘Jincheng’leaves were analyzed by qRT-PCR. The results showed that CsMEKK1-1 expression was downregulated by SA，JA and ETH and CLas-flg22 mainly down-regulated CsMEKK1-1 expression. To evaluate CsMEKK1-1 function，MEKK1-1 overexpression and RNA interference（RNAi）vectors were constructed，and were introduced into CLas-infected‘Jincheng’branches to generate transgenic hairy roots using Agrobacterium rhizogenes-mediated citrus transformation. Quantitative PCR analysis showed that CsMEKK1-1 positively promoted CLas proliferation in hairy roots，indicating that CsMEKK1-1 is a susceptible gene for HLB disease.

Key words: Citrus, Huanglongbing, MAPK signaling pathway, CsMEKK1-1, disease-susceptible gene

董丽婷, 屈荣荣, 庞淑炜, 莫凯琴, 陈爽, 商兰月, 邹修平. 柑橘CsMEKK1-1响应黄龙病菌侵染的表达特征与功能探究[J]. 园艺学报, 2024, 51(9): 2168-2182.

DONG Liting, QU Rongrong, PANG Shuwei, MO Kaiqin, CHEN Shuang, SHANG Lanyue, ZOU Xiuping. Expression Characteristics and Function Analysis of CsMEKK1-1 Gene in Response to Huanglongbing in Citrus[J]. Acta Horticulturae Sinica, 2024, 51(9): 2168-2182.

图/表 8

表1 研究中使用的引物

Table 1 Primers used in this study

引物名称 Primer ID	引物序列（5′-3′） Primer sequence
Cs_ont_1g020870 Cs_ont_6g014270 Cs_ont_3g009990	F：GCGGCTGAATCCAACTTTCG；R：GGAGGACCTCTCCTAGCCAT F：TGCTCCACTTCAAATGAGCTT；R：CGCAGGAGAAGTCCTACCAC F：CCGAGGTCGAGGTTGAAACA；R：TCAACTTGGTCCGAGTCAGC
Cs_ont_3g032130	F：TTTGGTGTAGCGCCATGGAT；R：AACGTGTTGACCCTGGTCTC
GAPDH HLBas HLBp	F：GCTTTCCGTGTACCCACTGT；R：CTCTGACTCCGCCTTGATGG F：TCGAGCGCGTATGCAATACG；R：GCGTTATCCCGTAGAAAAAGGTAG AGACGGGTGAGTAACGCG

图1 ‘锦橙’MAPK信号通路差异基因应答黄龙病菌感染的示意图红色表示上调，绿色表示下调，紫色表示上调或下调。“+P”表示磷酸化。病原感染英文后面的“O”表示感染病原体或生物体。

Fig. 1 Visualization of differentially expressed genes（DEGs）in MAPK pathway responding to CLas in‘Jincheng’oranges Red and green indicate up-regulated and down-regulated，purple indicate up-regulated and down-regulated respectively. “+P”indicates phosphorylation. The“O”after pathogen infection represents the infectious organism or organism.

图2 感染黄龙病（HLB）和未感染（对照）的‘锦橙’和‘马蜂柑’中MEKK1的相对表达量

Fig. 2 The relative expression levels of MEKK1 in‘Jincheng’and‘Mafenggan’infected with Huanglongbing（HLB）and uninfected（Control） * t-test，P < 0.05，n = 3.

图3 柑橘CsMEKK1-1的基因结构（A）、系统进化树（B）和编码蛋白序列（C）图B的数字表示节点的置信度，图C的数字表示图中的数字表示氨基酸残基的位置。 Cs：柑橘；Pt：杨树；Os：水稻；At：拟南芥；Hb：橡胶树；So：蒲桃；Mi：杧果；Jr：胡桃。

Fig. 3 Analysis of CsMEKK1-1 gene structures（A），phylogenetic tree（B）and protein sequence（C） The numbers in B indicate the confidence levels of the nodes，while the numbers in C represent the positions of the amino acid residues. Cs：Citrus sinensis；Pt：Populus tremula；Os：Oryza sativa；At：Arabidopsis thaliana；Hb：Hevea brasiliensis；So：Syzygium odoratum；Mi：Mangifera indica；Jr：Juglans regia.

图4 CsMEKK1-1蛋白在烟草表皮细胞中的亚细胞定位

Fig. 4 Subcellular location analysis of CsMEKK1-1 in tobacco epidermal cells

图5 ‘锦橙’叶圆片在外源SA、JA、ETH、ABA诱导下CsMEKK1-1的表达量

Fig. 5 Expression analysis of CsMEKK1-1 induced by SA，JA，ETH，ABA in‘Jincheng’orange * t-test，P < 0.05，n = 3.

图6 ‘锦橙’中CLas-flg22诱导下CsMEKK1-1的表达量

Fig. 6 Expression analysis of CsMEKK1-1 induced by CLas-flg22 in‘Jincheng’orange * t-test，P < 0.05，n = 3.

图7 带黄龙病菌的‘锦橙’转基因植株CsMEKK1-1表达量及病原菌含量 A：GFP荧光筛选；B：毛状根表型；C、D：毛状根CsMEKK1-1的PCR表达分析（M：Marker；+：阳性质粒对照；-：阴性对照）；E、F：叶片主脉和根系中的病原菌含量；EV：pNmGFPer空载对照；OE：CsMEKK1-1过表达转基因株系；RI：RNAi-CsMEKK1-1干扰株系。3次生物学重复，每重复样品来自3、4个根系。*表示与空载对照差异显著。

Fig. 7 Pathogen content and gene expression of CsMEKK1-1 transgenic plant‘Jincheng’infected with CLas A：GFP fluorescence screening. B：Hairy root phenotype. C and D：Identification of transgenic hairy roots by PCR（M：Marker；+：Positive plasmid；-：Negative control）；E and F：Bacterial content in midrib of leaves and roots；EV：pNmGFPer control；OE：OE-CsMEKK1-1 transgenic plants；RI：RNAi-CsMEKK1-1 transgenic plants. Three biological replicates，each sample comes from 3 or 4 roots. * indicates significant difference compared to the empty control.

参考文献 51

[1]	Andreasson E, Jenkins T, Brodersen P, Thorgrimsen S, Petersen N H T, Zhu S, Qiu J L, Micheelsen P, Rocher A, Petersen M. 2014. The MAP kinase substrate MKS 1 is a regulator of plant defense responses. EMBO Journal, 24 (14):2579-2589.
[2]	Bai Xiaojing, Xu Lanzhen, Jia Ruirui, Zhou Pengfei, Chen Min, He Yongrui, Peng Aihong, Lei Tiangang, Li Qiang, Yao Lixiao, Chen Shanchun, Zou Xiuping. 2017. Cloning and expression analysis of HLB-associated salicylic acid carboxyl methyltransferase gene CsSAMT-1 in citrus. Acta Horticulturae Sinica, 44 (12):2265-2274. (in Chinese) doi: 10.16420/j.issn.0513-353x.2017-0320
	白晓晶, 许兰珍, 贾瑞瑞, 周鹏飞, 陈敏, 何永睿, 彭爱红, 雷天刚, 李强, 姚利晓, 陈善春, 邹修平. 2017. 柑橘黄龙病相关水杨酸羧基甲基转移酶基因CsSAMT-1的克隆与表达分析. 园艺学报, 44 (12):2265-2274. doi: 10.16420/j.issn.0513-353x.2017-0320
[3]	Bailey T L, Mikael B, Buske F A, Martin F, Grant C E, Luca C, Jingyuan R, Li W W, Noble W S. 2009. MEME SUITE:tools for motif discovery and searching. Nucleic Acids Research,37 (Web Server issue):W202-W208.
[4]	Boller T, Felix G. 2009. A renaissance of elicitors:perception of microbe-associated molecular patterns and danger signals by pattern-recognition receptors. Annual Review of Plant Biology, 60 (1):379.
[5]	Brader G, Djamei A, Teige M, Palva E T, Hirt H. 2007. The MAP kinase kinase MKK 2 affects disease resistance in Arabidopsis. Mol Plant Microbe Interact, 20 (5):589-596.
[6]	Chen Xingtong, Du Chunmei. 2021. Advances in research on the phytohormone regulating interactions between plants and Fusarium oxysporum. Journal of Applied and Environmental Biology,27:816-822. (in Chinese)
	陈星彤, 杜春梅. 2021. 植物激素调控植物与尖孢镰刀菌的互作研究进展. 应用与环境生物学报,27:816-822.
[7]	Chinchilla D, Zipfel C, Robatzek S, Kemmerling B, Nurnberger T, Jones J D, Felix G, Boller T. 2007. A flagellin-induced complex of the receptor FLS2 and BAK 1 initiates plant defence. Nature, 448 (7152):497-500.
[8]	da Graa J V, Douhan G W, Halbert S E, Keremane M L, Lee R F, Vidalakis G, Zhao H W. 2016. Huanglongbing:An overview of a complex pathosystem ravaging the world’s citrus. Journal of Integrative Plant Biology,373-387.
[9]	Dan I, Watanabe N M, Kusumi A. 2001. The Ste 20 group kinases as regulators of MAP kinase cascades. Trends in Cell Biology, 11 (5):220-230. doi: 10.1016/s0962-8924(01)01980-8 pmid: 11316611
[10]	Dutt M, Barthe G, Irey M, Grosser J. 2015. Transgenic citrus expressing an Arabidopsis NPR1 gene exhibit enhanced resistance against Huanglongbing(HLB;Citrus Greening). PLoS ONE, 10 (9):e0147657.
[11]	Howe E S, Clemente T E, Bass H W. 2012. Maize Histone H2B-mCherry:a new fluorescent chromatin marker for somatic and meiotic chromosome research. DNA Cell Biol, 31 (6):925-938.
[12]	Gao Z, Zhang D, Wang X, Zhang X, Wen Z, Zhang Q, Li D, Dinesh-Kumar S P, Zhang Y. 2022. Coat proteins of necroviruses target 14-3-3a to subvert MAPKKK α-mediated antiviral immunity in plants. Nat Commun, 13 (1):716.
[13]	Gopalan S, Bauer D W, Alfano J R, Loniello A O, He S Y, Collmer A. 1996. Expression of the Pseudomonas syringae avirulence protein AvrB in plant cells alleviates its dependence on the hypersensitive response and pathogenicity (Hrp) secretion system in eliciting genotype-specific hypersensitive cell death. The Plant Cell, 8 (7):1095-1105.
[14]	Hao G X, Ammar D, Duan Y P, Stover E F. 2019. Transgenic citrus plants expressing a‘Candidatus Liberibacter asiaticus’prophage protein LasP₂₃₅ display Huanglongbing-like symptoms. Agri Gene,12:100085.
[15]	Guo Anyuan, Zhu Qihui, Chen Xin, Luo Jingchu. 2007. GSDS:a gene structure display server. Hereditas, 29 (8):1023-1026. (in Chinese)
	郭安源, 朱其慧, 陈新, 罗静初. GSDS:基因结构显示系统. 遗传, 29 (8):1023-1026.
[16]	Hirt C J A L. 2002. Complexity,Cross talk and integration of plant MAP kinase signalling. Current Opinion in Plant Biology,5:415-424.
[17]	Hong Y, Liu Q, Cao Y, Zhang Y, Chen D, Lou X, Cheng S, Cao L. 2019. The OsMPK15negatively regulates Magnaporthe oryza and Xoo disease resistance via SA and JA signaling pathway in rice. Frontiers in Plant Science,10:752.
[18]	Hu B, Rao M J, Deng X, Pandey S S, Hendrich C, Ding F, Wang N, Xu Q. 2021. Molecular signatures between citrus and Candidatus Liberibacter asiaticus. PLoS Pathog, 17 (12):e1010071.
[19]	Jiang M, Wen F, Cao J, Li P, She J, Chu Z Q. 2015. Genome-wide exploration of the molecular evolution and regulatory network of mitogen-activated protein kinase cascades upon multiple stresses in Brachypodium distachyon. BMC Genomics, 16 (1):228.
[20]	Jouannic S, Hamal A, Leprince A S, Tregear J W, Kreis M, Henry Y. 1999. Characterisation of novel plant genes encoding MEKK/STE11 and RAF-related protein kinases. Gene, 229 (1-2):171-181. doi: 10.1016/s0378-1119(99)00012-8 pmid: 10095117
[21]	Lee H Y, Back K. 2016. Mitogen-activated protein kinase pathways are required for melatonin-mediated defense responses in plants. Journal of Pineal Research, 60 (3):327-335. doi: 10.1111/jpi.12314 pmid: 26927635
[22]	Li Jia. 2012. Isolation and characterization of endophytic bacteria from Huanglongbing’s host plant-Murraya paniculata and Catharanthus roseus[Ph. D. Dissertation]. Chongqing: Chongqing University. (in Chinese)
	李佳. 2012. 柑橘黄龙病寄主植物内生细菌多样性分析及相关性研究[博士论文]. 重庆: 重庆大学.
[23]	Li W, Hartung J S, Levy L. 2006. Quantitative real-time PCR for detection and identification of Candidatus Liberibacter species associated with citrus Huanglongbing. Microbiol Methods, 66 (1):104-115.
[24]	Li X, Ruan H, Zhou C, Meng X, Chen W. 2021. Controlling citrus Huanglongbing:green sustainable development route is the future. Frontiers in Plant Science,12:760481.
[25]	Livak K J, Schmittgen T D. 2001. Analysis of relative gene expression data using real-time quantitative PCR and the 2^-ΔΔCT method. Methods, 25,402-408. doi: 10.1006/meth.2001.1262 pmid: 11846609
[26]	Liu X, Li J, Noman A, Lou Y. 2019. Silencing OsMAPK20-5 has different effects on rice pests in the field. Plant Signaling & Behavior, 14 (9):1-3.
[27]	Liu Y N, Dong L T, Ran D L, Wang S, Qu R R, Zheng L, Peng A H, He Y R, Chen S C, Zou X P. 2023. A comparative analysis of three Rutaceae species reveals the multilayered mechanisms of Citrus in response to Huanglongbing disease. Journal of Plant Growth Regulation, 42 (12):7564-7579.
[28]	Medina-Puche L, Tan H, Dogra V, Wu M, Rosas-diaz T, Wang L P, Ding X, Zhang D, Fu X, Kim C, Lozano-Duran R. 2020. A defense pathway linking plasma membrane and chloroplasts and co-opted by pathogens. Cell, 182 (5):1109. doi: S0092-8674(20)30885-0 pmid: 32841601
[29]	Melech-Bonfil S, Sessa G. 2010. Tomato MAPKKKε is a positive regulator of cell-death signaling networks associated with plant immunity. Blackwell Publishing Ltd,64 (3):379-391.
[30]	Meng X Z, Zhang S Q. 2013. MAPK cascades in plant disease resistance signaling. Annual Review of Phytopathology,51:245-266.
[31]	Ogata H, Goto S, Sato K, Fujibuchi W, Kanehisa M. 1999. KEGG:kyoto encyclopedia of genes and genomes. Nucleic Acids Research, 27 (1):29-34. doi: 10.1093/nar/27.1.29 pmid: 9847135
[32]	Oka K, Amano Y, Katou S, Seo S, Kawazu K, Mochizuki A, Kuchitsu K, Mitsuhara I. 2013. Tobacco MAP kinase phosphatase (NtMKP1) negatively regulates wound response and induced resistance against necrotrophic pathogens and lepidopteran herbivores. Mol Plant Microbe Interact, 26 (6):668-675.
[33]	Pedley K F, Martin G B. 2004. Identification of MAPKs and their possible MAPK kinase activators involved in the Pto-mediated defense response of tomato. The Journal of Biological Chemistry, 279 (47):49229.
[34]	Peng A, Zou X, He Y, Chen S, Zhao X. 2021. Overexpressing a NPR1-like gene from Citrus paradisi enhanced Huanglongbing resistance in C. sinensis. Plant Cell Reports, 40 (3):529-541.
[35]	Ribeiro C, Xu J, Hendrich C, Pandey S S, Yu Q, Gmitter F J, Wang N. 2023. Seasonal transcriptome profiling of susceptible and tolerant citrus cultivars to citrus Huanglongbing. Phytopathology, 113 (2):286-298.
[36]	Shi Q, Febres V J, Zhang S, Yu F, Stover E. 2018. Identification of gene candidates associated with Huanglongbing tolerance,using Candidatus liberibacter asiaticus flagellin 22 as a proxy to challenge citrus. Molecular Plant-Microbe Interactions, 31 (2):200.
[37]	Singh R, Lee J E, Dangol S, Choi J, Yoo R H, Moon J S, Shim J K, Rakwal R, Agrawal G K, Jwa N S. 2014. Protein interactome analysis of 12 mitogen‐activated protein kinase kinase kinase in rice using a yeast two-hybrid system. Proteomics, 14 (1):105-115.
[38]	Song F, Goodman R M. 2002. OsBIMK1,a rice MAP kinase gene involved in disease resistance responses. Planta, 215 (6):997-1005.
[39]	Tena G, Boudsocq M, Sheen J. 2011. Protein kinase signaling networks in plant innate immunity. Current Opinion in Plant Biology,14:519-29.
[40]	Wang Miaomiao. 2018. Identification and genetic transformation of citrus MAPK genes and PR genes induced by Huanglongbing[Ph. D. Dissertation]. Chongqing: Southwest University. (in Chinese)
	王苗苗. 2018. 响应柑橘黄龙病的MAPK基因和PR基因鉴定及遗传转化[博士论文]. 重庆: 西南大学.
[41]	Wang Gang. 2014. Identification,expression analysis of MAPK-like gene families in grapevine and functional characteration of some members[Ph. D. Dissertation]. Nanjing: Nanjing Agricultural University. (in Chinese)
	王刚. 2014. 葡萄MAPK类基因家族的鉴定、表达分析及部分基因的功能验证[博士论文]. 南京: 南京农业大学.
[42]	Xiong L. 2003. Disease resistance and abiotic stress tolerance in rice are inversely modulated by an abscisic acid-inducible mitogen-activated protein kinase. The Plant Cell, 15 (3):745-759.
[43]	Yu Q, Chen C, Du D, Huang M, Yao J, Yu F, Brlansky R H, Gmitter F G. 2017. Reprogramming of a defense signaling pathway in rough lemon and sweet orange is a critical element of the early response to‘Candidatus Liberibacter asiaticus’. Horticulture Research,4:17063.
[44]	Yu Xinxin, Gao Jinjun, Li Yong, Li Jing. 2014. Transcriptome analysis of Arabidopsis thaliana and changes of glucosinolates metabolism pathway induced by Flg22. China biotechnology, 34 (5):30-38. (in Chinese)
	于欣鑫, 高晋君, 李勇, 李晶. 2014. flg22诱导的拟南芥转录组分析及芥子油苷代谢途径的变化. 中国生物工程杂志, 34 (5):30-38.
[45]	Zhao Ke, Zheng Lin, Du Meixia, Long Junhong, He Yongrui, Chen Shanchun, Zou Xiuping. 2021. Response characteristics of plant SAR and its signaling gene CsSABP2 to Huanglongbing infection in citrus. Scientia Agricultura Sinica, 54 (8):1638-1652. (in Chinese)
	赵珂, 郑林, 杜美霞, 龙俊宏, 何永睿, 陈善春, 邹修平. 2021. 柑橘SAR及其信号转导基因CsSABP2在黄龙病菌侵染中的响应特征. 中国农业科学, 54 (8):1638-1652. doi: 10.3864/j.issn.0578-1752.2021.08.006
[46]	Zheng Lin, Wang Shuai, Liu Yunuo, Du Meixia, Peng Aihong, He Yongrui, Chen Shanchun, Zou Xiuping. 2022. Gene cloning and expression analysis of NAC gene in citrus in response to Huanglongbing. Acta Horticulturae Sinica, 49 (7):1441-1457. (in Chinese) doi: 10.16420/j.issn.0513-353x.2021-0553
	郑林, 王帅, 刘语诺, 杜美霞, 彭爱红, 何永睿, 陈善春, 邹修平. 2022. 柑橘响应黄龙病菌侵染的NAC基因的克隆及表达分析. 园艺学报, 49 (7):1441-1457. doi: 10.16420/j.issn.0513-353x.2021-0553
[47]	Zhou J M. 2010. Plant immunity triggered by microbial molecular signatures. Molecular Plant, 3 (5):783-793. doi: 10.1093/mp/ssq035 pmid: 20713980
[48]	Zou Jiajun. 2015. Gene structure and transcriptional regulation ófmitogen-activated protein kinase kinases(MAPKK) of Yesso scallop Patinopecten yessoensis[M. D. Dissertation]. Qingdao: Ocean University of China. (in Chinese).
	邹佳君. 2015. 虾夷扇贝(Patinopecten yessoensis)MAPKK基因家族结构及表达分析[硕士论文]. 青岛: 中国海洋大学.
[49]	Zou X, Jiang X, Xu L, Lei T, Peng A, He Y, Yao L, Chen S. 2017. Transgenic citrus expressing synthesized cecropin B genes in the phloem exhibits decreased susceptibility to Huanglongbing. Plant Molecular Biology, 93 (4-5):1-13.
[50]	Zou X, Zhao K, Liu Y, Du M, Zheng L, Wang S, Xu L, Peng A, He Y, Long Q. 2021. Overexpression of salicylic acid carboxyl methyltransferase (CsSAMT1) enhances tolerance to Huanglongbing disease in Wanjincheng orange[Citrus sinensis(L.)Osbeck]. International Journal of Molecular Sciences, 22 (6):2803.
[51]	Zou X P, Long J H, Zhao K, Peng A H, Chen M, Long Q, He Y R, Chen S C. 2019. Overexpressing GH3.1 and GH3.1L reduces susceptibility to Xanthomonas citri subsp. citri by repressing auxin signaling in citrus(Citrus sinensis Osbeck). PLoS ONE,14:22.