Plastid KEA-type cation/H+ antiporters are required for vacuolar protein trafficking in Arabidopsis

Arabidopsis plastid antiporters KEA1 and KEA2are critical for plastid development, photosynthetic efficiency, and plant development.Here, we show that KEA1 and KEA2 are involved in vacuolar protein trafficking. Genetic analyses found that the kea1 kea2 mutants had short siliques, small seeds, and short seedlings. Molecular and biochemical assays showed that seed storage proteins were missorted out of the cell and the precursor proteins were accumulated in kea1 kea2. Protein storage vacuoles(PSVs) were smaller in kea1 kea2. Further analyses showed that endosomal trafficking in kea1 kea2 was compromised. Vacuolar sorting receptor 1(VSR1) subcellular localizations, VSR–cargo interactions, and p24 distribution on the endoplasmic reticulum(ER) and Golgi apparatus were affected in kea1 kea2. Moreover, plastid stromule growth was reduced and plastid association with the endomembrane compartments was disrupted in kea1 kea2. Stromule growth was regulated by the cellular pH and K+homeostasis maintained by KEA1 and KEA2. The organellar pH along the trafficking pathway was altered in kea1 kea2. Overall, KEA1 and KEA2 regulate vacuolar trafficking by controlling the function of plastid stromules via adjusting pH and K+homeostasis.

Plant and Yeast NHX Antiporters: Roles in Membrane Trafficking

The plant NHX gene family encodes Na＋/H＋ antiporters which are crucial for salt tolerance, potassium homeostasis and cellular pH regulation. Understanding the role of NHX antiporters in membrane trafficking is becoming an increasingly interesting subject of study. Membrane trafficking is a central cellular process during which proteins, lipids and polysaccharides are continuously exchanged among membrane compartments. Yeast ScNhxlp, a prevacuole/ vacuolar Na＋/H＋ antiporter, plays an important role in regulating pH to control trafficking out of the endosome. Evidence begins to accumulate that plant NHX antiporters might function in regulating membrane trafficking in plants.

V-ATPase,ScNhxlp and Yeast Vacuole Fusion

Membrane fusion is the last step in trafficking pathways during which membrane vesicles fuse with target organelles to deliver cargos. It is a central cellular reaction that plays important roles in signal transduction, protein sorting and subcellular compartmentation. Recent progress in understanding the roles of ion transporters in vacuole fusion in yeast is summarized in this article. It is becoming increasingly evident that the vacuolar proton pump V-ATPase and vacuolar Na＋/H＋ antiporter ScNhxlp are key components of the vacuole fusion machinery in yeast. Yeast ScNhxlp regulates vacuole fusion by controlling the luminal pH. V-ATPases serve a dual role in vacuolar integrity in which they regulate both vacuole fusion and fission reactions in yeast. Fission defects are epistatic to fusion defects. Vacuole fission depends on the proton translocation activity of the V-ATPase; by contrast, the fusion reaction does not need the transport activity but requires the physical presence of the proton pump. V0, the membrane-integral sector of the V-ATPase, forms trans-complexes between the opposing vacuoles in the terminal phase of vacuole fusion where the V0 trans-complexes build a continuous proteolipid channel at the fusion site to mediate the bilayer fusion.

Plant genome editing:CRISPR,base editing,prime editing,and beyond

The clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated protein 9(Cas9)system is a fast-growing,genome editing technology that has wide applications in identifying gene functions as well as improving agricultural production and crop breeding.Here,we summarized recent advances in the development and applications of genome editing technologies in plants.We briefly described CRISPR/Cas9 technology and examined the base and prime editing techniques that have been developed from CRISPR technology.Some new prime editing-derived techniques were assessed.