Abstract
The current model for vesicular traffic to and from the plasma membrane is accepted, but the molecular requirements for this coordination are not well defined. We have identified the hot ABA-deficiency suppressor1 mutant, which has a stomatal function defect, as a clathrin heavy chain1 (CHC1) mutant allele and show that it has a decreased rate of endocytosis and growth defects that are shared with other chc1 mutant alleles. We used chc1 alleles and the related chc2 mutant as tools to investigate the effects that clathrin defects have on secretion pathways and plant growth. We show that secretion and endocytosis at the plasma membrane are sensitive to CHC1 and CHC2 function in seedling roots and that chc mutants have physiological defects in stomatal function and plant growth that have not been described previously. These findings suggest that clathrin supports specific functions in multiple cell types. Stomata movement and gas exchange are altered in chc mutants, indicating that clathrin is important for stomatal regulation. The aberrant function of chc mutant stomata is consistent with the growth phenotypes observed under different water and light conditions, which also are similar to those of the secretory SNARE mutant, syp121 The syp121 and chc mutants have impaired endocytosis and exocytosis compared with the wild type, indicating a link between SYP121-dependent secretion and clathrin-dependent endocytosis at the plasma membrane. Our findings provide evidence that clathrin and SYP121 functions are important for the coordination of endocytosis and exocytosis and have an impact on stomatal function, gas exchange, and vegetative growth in Arabidopsis (Arabidopsis thaliana).
Highlights
The current model for vesicular traffic to and from the plasma membrane is accepted, but the molecular requirements for this coordination are not well defined
The has1 mutant was originally identified in an infrared imaging screen of a g-ray mutagenized population of the abscisic acid (ABA) deficient3 mutant
We reduced the interval to 0.4 Mb, and next-generation DNA sequencing of has1 identified a five-nucleotide deletion in the 23rd exon of the clathrin heavy chain1 (CHC1) gene (At3g11130) that introduces a frame shift and produces a premature stop codon into the CHC1 gene (Supplemental Fig. S1)
Summary
The current model for vesicular traffic to and from the plasma membrane is accepted, but the molecular requirements for this coordination are not well defined. We show that secretion and endocytosis at the plasma membrane are sensitive to CHC1 and CHC2 function in seedling roots and that chc mutants have physiological defects in stomatal function and plant growth that have not been described previously These findings suggest that clathrin supports specific functions in multiple cell types. Exocytosis facilitates the distribution of proteins such as ion channels, receptors, and transporters to the cell surface at specific times and regions of the plasma membrane; it provides a mechanism for delivering cell wall components to the Exocytic pathways to the plasma membrane are complemented by endocytic traffic that removes and recycles proteins and lipids from the plasma membrane, thereby regulating their presence and activity (Becker et al, 2003; Dhonukshe et al, 2007; Sutter et al, 2007; Kitakura et al, 2011) This other side of the traffic cycle at the plasma membrane is critical for physiology and development. While all evidence supports a requirement for vesicle traffic in stomatal function, it is not clear how the two sides of the trafficking cycle to and from the guard cell plasma membrane are linked
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