Manganese (Mn) is one of the essential micronutrient elements and is necessary for plant growth and development. Most studies on the physiological mechanisms of plant responses to Mn toxicity were focused on Mn-inhibited photosynthesis, Mn-mediated changes in antioxidative enzymes, and reactive oxygen species production. However, whether and how Mn toxicity affects root growth by mediating auxin distribution and response in roots remains poorly understood.
Prof. XU Jin and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to investigate the role of auxin in Mn-mediated inhibition of primary root (PR) growth in Arabidopsis using physiological and genetic approaches. They characterized Mn-inhibited root growth and described altered patterns of auxin accumulation and distribution in the PR of Mn-treated roots.
Wild-type Arabidopsis col-0 was used in their study. The following mutant and transgenic Arabidopsis lines were used: pin4-3, pin7-2, and DR5:GUS, DII-VENUS, PIN1:PIN1-GFP, PIN2:PIN2-GFP, PIN4:PIN4-GFP, PIN7:PIN7-GFP, AUX1:AUX1-YFP, CYCB1;1:GUS.
They found that Mn toxicity reduced DR5:GUS expression whereas it increased DII-VENUS fluorescent signal in the root tips, indicating that exposure to excess Mn resulted in PR growth inhibition by reducing auxin accumulation in root tips.
Mn toxicity decreased auxin accumulation in roots by reducing auxin biosynthesis and repressing auxin transport via the decrease of the expression of auxin efflux carriers PIN4 and PIN7.
Loss of function pin4 and pin7 mutants showed less inhibition of root growth than col-0 seedlings.
Their study indicates that Mn toxicity inhibited PR growth by reducing auxin biosynthesis and repressing the expression of auxin efflux transporters PIN4 and PIN7 to reduce auxin levels in root tips, resulting in reduced root meristematic cell division.
XU Jin, Ph.D Principal Investigator Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China E-mail: email@example.com Tel: +86 871 65140420
Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences. Menglun, Mengla, Yunnan 666303, China
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