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Journal of Integrative Agriculture  2025, Vol. 24 Issue (6): 2035-2045    DOI: 10.1016/j.jia.2024.04.007
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OsEXO70L2 is required for large lateral root formation and arbuscular mycorrhiza establishment in rice
Tongming Wang1, Kai Zhou1, Bingxian Yang2, Benoit Lefebvre 1, 3#, Guanghua He1#

1 Chongqing Key Laboratory of Crop Molecular Improvement/Rice Research Institute, Academy of Agricultural Sciences, Southwest University, Chongqing 400715, China

2 College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou 310018, China

3 Laboratory of Plant–Microbe–Environment Interactions (LIPME), University of Toulouse, INRAE, CNRS, Castanet-Tolosan Cedex 31326, France

 Highlights 
● Formation of large lateral roots is inhibited in Oryza sativa EXO70L2 mutant sr1.
EXO70L2 mutant in indica cultivar Jinhui 10 is unable to establish arbuscular mycorrhizal symbiosis.
● Arbuscular mycorrhizal fungi sporulation is influenced by light conditions.
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摘要  
EXO70家族蛋白是组成胞泌复合体的关键亚基,该家族的部分成员在拟南芥中被证明主要在细胞极性和形态建成过程中发挥关键作用,但EXO70蛋白在植物菌根共生方面的研究却鲜有报道。我们在水稻中鉴定了一个在进化关系上偏离EXO70家族的基因OsEXO70L2,并获得其突变体sr1和超表达株系OE-SR1。研究结果表明,OsEXO70L2参与调控水稻根系构型,不仅影响初生根的数量,而且对大侧根的形成至关重要。接种丛枝真菌后,OsEXO70L2突变体根系中丛枝真菌无法正常定殖,但可以观察到极少量的内生菌丝。我们还发现,尽管水稻根系中丛枝菌根的定殖量较低,但丛枝真菌孢子化现象仍然可以发生,并且光照周期能显著影响丛枝真菌的定殖量和孢子化位点的数量;存在护士植物时,OsEXO70L2突变体也无法被丛枝真菌正常定殖,但根内孢子的密度显著增加。结合转录组学数据,在OsEXO70L2突变体和超表达株系中,与生长素稳态相关基因的表达量受到影响,这表明OsEXO70L2可能通过调节生长素稳态影响水稻根系构型,最终影响菌根的定殖。该研究丰富了EXO70蛋白家族成员的生物学功能,为探究水稻胞泌复合体与丛枝真菌共生的关系奠定了理论基础。


Abstract  

As a major subunit of the exocyst complex, members of the EXO70 family have mainly been shown to play roles in cell polarity and morphogenesis in Arabidopsis, but their roles in plant endosymbiosis, such as with arbuscular mycorrhizal fungi (AMF), have rarely been reported.  Here, using knockout and overexpression lines, we show that OsEXO70L2, which encodes a divergent EXO70 protein in rice, controls the number of primary roots and is essential for large lateral root formation.  Furthermore, the OsEXO70L2 mutant sr1 displayed rare internal AMF hyphae and no arbuscules.  We also found that AMF sporulation can occur in roots despite low colonization and that AMF colonization and sporulation are modulated by photoperiod and co-culture with clover.  Finally, genes related to auxin homeostasis were found to be affected in the OsEXO70L2 knockout or overexpression lines, suggesting that auxin is at least partly responsible for the phenotypes.  This study provides new perspectives on the role of the exocyst complex during root development and AM in rice.

Keywords:  rice        EXO70        root formation        arbuscular mycorrhizal        sporulation  
Received: 16 January 2024   Online: 10 April 2024   Accepted: 11 March 2024
Fund: 
This work was supported by the National Natural Science Foundation of China (32171970), the Chongqing Talent Program, China (cstc2022ycjh-bgzxm0073), the Natural Science Foundation of Chongqing, China (cstc2021jcyj-cxttX0004), and the Rice Innovative Research Team of Chongqing Modern Agricultural Industrial Technology System, China (CQMAITS202301). 
About author:  #Correspondence Guanghua He, Tel/Fax: +86-23-68250158, E-mail: heghswu@163.com; Benoit Lefebvre, Tel/Fax: +33-5-61285322, E-mail: benoit.lefebvre@inrae.fr

Cite this article: 

Tongming Wang, Kai Zhou, Bingxian Yang, Benoit Lefebvre, Guanghua He. 2025. OsEXO70L2 is required for large lateral root formation and arbuscular mycorrhiza establishment in rice. Journal of Integrative Agriculture, 24(6): 2035-2045.

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