Significance
Roots and shoots communicate with each other to synchronize
and optimize plant growth and respond to environmental
changes. Shoots and roots exchange signals to sense the status
and respond to the needs of the other organ. Cytokinins, which
are phytohormones that regulate various aspects of growth
and development, are recognized as the most important signal
transmitted from roots to shoots. Whereas the enzymes underlying
cytokinin biosynthesis and the corresponding receptors
have been identified, our knowledge of cytokinin transport
is limited. In this study, we identified the Arabidopsis ATPbinding
cassette transporter subfamily G14 as a major component
in the transfer of cytokinins from roots to shoots and
hence as a regulator of shoot development. This finding
represents a major breakthrough in the field.