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New Tonoplast Proton Pumps Function Revealed in Arabidopsis Embryo Development

October 12, 2019      Author:

On September 30, 2019, Prof. Wen-Hui Lin's group published an article entitled " Two Tonoplast Proton Pumps Function in Arabidopsis Embryo Development" in New Phytologist. This work revealed that two types of proton pumps regulated plant embryo development and pattern formation through influencing vacuole morphology and auxin signaling. This study demonstrated the new function of vacuole in plant development and closely linked vacuole morphology, hormonal signaling, and developmental processes.

In Arabidopsis, two types of tonoplast proton pumps, H+-pyrophosphatase (V-PPase) and the H+-ATPase (V-ATPase), establish the proton gradient that powers molecular traffic across tonoplast thereby facilitating turgor regulation and nutrient homeostasis. But the regulatory mechanism of their funtion in plant growth and development still remained unclear. In this study, the authors analysis detailed phenotypes of two different alleles lacking both V-ATPase and V-PPase (vap3 and fap3). While disruption of either V-PPase or V-ATPase had no obvious effect on plant embryo development, knocking out both resulted in severe defects in embryo development and pattern formation from very beginning and lead to severe abnormal pattern of cotyledons. Further observation illustrated the abnormal vacuole morphology and distribution in embryo and suspensor cells of triple mutants, indicating the tight link between vacuole morphology and defects of embryonic cell division and pattern formation.

Pattern formation of embryogenesis, especially cotyledon primordia initiation and development, was known to be determined by auxin signaling. The abnormal cotyledons in triple mutants revealed the disturbed auxin polar transportation. The authors thus examined the auxin responses of triple mutants and found vap3/fap3 mutants were apparently less sensitive to gravity, exogenous auxin and the inhibitor or auxin polar transport. PIN1 protein (the main transporter of auxin) level and auxin content were also affected in vap3. PIN1 protein distribution was largely insensitive to BFA-treatment by lacking both of tonoplast proton pumps, suggesting the abnormal Intracellular transport of PIN1 protein. The authors further found the vacuole size and morphology were obviously changed in seedling root of triple mutants and the pH value of vacuole was higher in triple mutants than wild type. The above results demonstrated that lacking both of tonoplast proton pumps affected cell size and vacuole size, morphology and acidification.

Taking together, this research propose two tonoplast proton pumps are required for vacuole morphology and PIN1 localization thereby controlling vacuole and auxin related developmental processes in Arabidopsis embryos and seedlings.

  PhD student of Lin group, Yu-Tong Jiang, is the first author of this paper. Prof. Wen-Hui Lin is the corresponding author, Prof. Sheng Luan from University of California at Berkeley is the co-corresponding author. The work was supported by Natural Science Foundation of China, the National Science Foundation of U.S.A., the CSC Scholarship, and the Opening Research Projects of National Key Laboratory of Plant Molecular Genetics, SIPPE, CAS.

 

 Source: School of Life Sciences and Biotechnology