J Integr Plant Biol. ›› 2023, Vol. 65 ›› Issue (3): 721-738.DOI: 10.1111/jipb.13393

• Cell and Developmental Biology • Previous Articles     Next Articles

IQ67 DOMAIN protein 21 is critical for indentation formation in pavement cell morphogenesis

Xinhua Feng1, Shujuan Pan1, Haifu Tu1, Junjie Huang2, Chuanlei Xiao1, Xin Shen1, Lei You1, Xinyan Zhao3, Yongqiang Chen1, Danyun Xu1, Xiaolu Qu4 and Honghong Hu1*   

  1. 1. National Key Laboratory of Crop Genetic Improvement, Hubei Hongshan Laboratory, Huazhong Agricultural University, Wuhan 430070, China;
    2. Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Wuhan University, Wuhan 430070, China;
    3. Shanghai Center for Plant Stress Biology, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 201602, China;
    4. Key Laboratory of Horticultural Plant Biology (MOE), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China
    *Correspondence: Honghong Hu (huhh@mail.hzau.edu.cn)
  • Received:2022-08-04 Accepted:2022-10-15 Online:2022-10-20 Published:2023-03-01

Abstract: In plants, cortical microtubules anchor to the plasma membrane in arrays and play important roles in cell shape. However, the molecular mechanism of microtubule binding proteins, which connect the plasma membrane and cortical microtubules in cell morphology remains largely unknown. Here, we report that a plasma membrane and microtubule dual-localized IQ67 domain protein, IQD21, is critical for cotyledon pavement cell (PC) morphogenesis in Arabidopsis. iqd21 mutation caused increased indentation width, decreased lobe length, and similar lobe number of PCs, whereas IQD21 overexpression had a different effect on cotyledon PC shape. Weak overexpression led to increased lobe number, decreased indentation width, and similar lobe length, while moderate or great overexpression resulted in decreased lobe number, indentation width, and lobe length of PCs. Live-cell observations revealed that IQD21 accumulation at indentation regions correlates with lobe initiation and outgrowth during PC development. Cell biological and genetic approaches revealed that IQD21 promotes transfacial microtubules anchoring to the plasma membrane via its polybasic sites and bundling at the indentation regions in both periclinal and anticlinal walls. IQD21 controls cortical microtubule organization mainly through promoting Katanin 1-mediated microtubule severing during PC interdigitation. These findings provide the genetic evidence that transfacial microtubule arrays play a determinant role in lobe formation, and the insight into the molecular mechanism of IQD21 in transfacial microtubule organization at indentations and puzzle-shaped PC development.

Key words: IQD21, KTN1, lobe outgrowth, pavement cell interdigitation, transfacial microtubules

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