Slowing Development Facilitates Arabidopsis mgt Mutants to Accumulate Enough Magnesium for Pollen Formation and Fertility Restoration

Abstract

Magnesium (Mg) is an abundant and important cation in cells. Plants rely on Mg transporters to take up Mg from the soil, and then Mg is transported to anthers and other organs. Here, we showed that <i>MGT6+/-</i> plants display reduced fertility, while <i>mgt6</i> plants are fertile. <i>MGT6</i> is expressed in the anther at the early stages. Pollen mitosis and intine formation are impaired in aborted pollen grains (PGs) of <i>MGT6+/-</i> plants, which is similar to the defective pollen observed in <i>mgt5</i> and <i>mgt9</i> mutants. These results suggest that Mg deficiency leads to pollen abortion in <i>MGT6+/-</i> plants. Our data showed that <i>mgt6</i> organs including buds develop significantly slower and <i>mgt6</i> stamens accumulate a higher level of Mg, compared with wild-type (WT) and <i>MGT6+/-</i> plants. These results indicate that slower bud development allows <i>mgt6</i> to accumulate sufficient amounts of Mg in the pollen, explaining why <i>mgt6</i> is fertile. Furthermore, we found that <i>mgt6</i> can restore fertility of <i>mgt5</i>, which has been reported to be male sterile due to defects in Mg transport from the tapetum to microspores and that an additional Mg supply can restore its fertility. Interestingly, <i>mgt5</i> fertility is recovered when grown under short photoperiod conditions, which is a well-known factor regulating plant fertility. Taken together, these results demonstrate that slow development is a general mechanism to restore <i>mgt</i>s fertility, which allows other redundant magnesium transporter (MGT) members to transport sufficient Mg for pollen formation.