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Stromule extension along microtubules coordinated with actin-mediated anchoring guides perinuclear chloroplast

Amutha Sampath Kumar1, Eunsook Park2,3, Alexander Nedo1,4

  • 1Delaware Biotechnology Institute, University of Delaware, Newark, United States.

Elife
|January 18, 2018
PubMed

Insights

Stromules, dynamic chloroplast extensions, move along microtubules and connect to actin filaments. This movement guides chloroplasts toward the nucleus, especially during innate immunity responses.

Area of Science:

  • Plant cell biology
  • Molecular plant pathology

Background:

  • Chloroplasts possess dynamic tubular extensions called stromules.
  • Stromules have been implicated in connecting with nuclei and playing a role in innate immunity.

Purpose of the Study:

  • To investigate the role of cytoskeletal elements, specifically microtubules (MTs) and actin filaments (AFs), in stromule dynamics and chloroplast movement.
  • To elucidate the mechanism by which stromules facilitate chloroplast-nucleus interactions during innate immunity.

Main Methods:

  • Chemical and genetic stabilization of microtubules.
  • Observation of stromule dynamics and chloroplast movement in epidermal cells.
  • Analysis of the correlation between stromule direction and chloroplast movement.

Main Results:

  • Stromule extension is dependent on microtubules (MTs); MT stabilization increases stromule number and length.
  • Actin filaments (AFs) are not essential for stromule extension but serve as anchor points.
  • A strong correlation exists between stromule direction and chloroplast movement, observed even without immune induction.
  • MTs and AFs may facilitate perinuclear clustering of chloroplasts during innate immune responses.

Conclusions:

  • Microtubules provide tracks for stromule extension, while actin filaments offer anchoring.
  • Stromules actively direct chloroplast movement towards the nucleus, a function observed in steady-state and during innate immunity.
  • A model is proposed where MT- and AF-associated stromules guide chloroplasts to the nucleus for innate immunity signaling.
Keywords:
Nicotiana benthamianacell biologychloroplastscytoskeletonorganelle movementplant biologyplant innate immunitystromules

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