Water deficit severely reduces apple growth and production and is
detrimental to fruit quality and size. Thus, water-efficiency became the
major target for apple breeding. Aquaporins control water transport across
membranes and can regulate water flow by changing their amount and activity.
The exploration of molecular mechanism of water efficiency will pave a way
for breeding of drought tolerant apple trees.

Lin Wang of China Agricultural University, together with a team of
researchers, focused on an apple (Malus domestica) drought inducible
aquaporin gene, MdPIP1;3. The team expressed MdPIP1;3 gene in tomato. The
transgenic tomatoes exhibited enhanced drought stress tolerance, indicating
that water loss rate in transgenic leaves was slower than wild types.

The lengths and diameters of the transgenic tomato fruits increased faster
that the wild types. Final fruit sizes and fresh weights of the transgenic
tomatoes were also bigger and higher than wild types. In cell levels, fruit
cell size from transgenic tomatoes was also larger.

Expressing MdPIP1;3 enhanced drought tolerance of transgenic tomatoes,
partially by reducing water loss in leaves. The transgenic tomato fruits
were also larger and heavier due to larger cells via more efficient water
transport across membranes.



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