Salination causes harvests to fail across the globe. Plants die, or their growth is stunted. Researchers of Wageningen University & Research (WUR) have discovered that a local regulator protein encourages root growth in saline soil, which allows the plant to develop under these adverse conditions. The findings have been published in the scientific journal the Plant Cell and form a critical basis for further research into the development of more resilient crop varieties.
Almost one-quarter of all irrigated farmlands are affected by salination. Rising sea levels, increasing drought, and rising temperatures exacerbate this issue. Saline soil has a detrimental effect on the development of lateral roots, says plant physiology professor Christa Testerink. 'Plants need lateral roots to absorb water and nutrients. The hormone that regulates the growth of lateral roots is called auxin. Salt hampers the plant's ability to recognize the signals this hormone emits, causing the development of lateral roots to fall short. And fewer lateral roots means the plant's general health suffers.'
Switch between hormone and lateral root growth
How is it that some plant species are less affected by salinity stress than others? To answer this question, researchers delved into the molecular mechanism that drives root development in the model plant Arabidopsis, commonly known as thale cress. Testerink: 'Previous research already revealed that the protein LBD16 serves as a switch between the plant hormone auxin and the development of lateral roots. LBD16 activates the genes responsible for the development of lateral roots. In saline soil, you would expect auxin's functioning to become impaired, but you would also expect the levels of the LBD16 protein to drop.'
Alternative route discovered
Surprisingly, research showed that the functioning of auxin was severely reduced in thale cress in a saline environment, while the levels of LBD16 rose. Testerink: 'This suggests an alternative route driving the protein, which enables the plant to still produce, albeit fewer, lateral roots in saline conditions. We succeeded in finding this route by uncovering another activator, the ZAT6 protein. This protein takes over auxin's role as regulator. This discovery provides a critical basis for further studies into similar local molecular networks in lateral roots that help plants function in stressful situations. Not just under saline conditions but also in times of drought or heat. This could help plant breeders to alter the plants' root growth to create more resilient varieties.'
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