The legume-rhizobium symbiotic relationship has been widely studied and
characterized. However, little information is known on the role of histone
lysine methyltransferases in this interaction and in the formation of
nodules in the common bean.
A study by the team of Aarón Barraza from Centro de Investigación y de
Estudios Avanzados del Instituto Politécnico Nacional aimed to understand
the mechanism of nodulation control in common bean (Phaseolus vulgaris). The
team focused on the role of PvTRX1h, a histone lysine methyltransferase
coding gene, in nodule development, and auxin biosynthesis. Using reverse
genetics approach, the team generated common bean with knocked-down PvTRX1h
Downregulation of PvTRX1h increased the number of nodules per plant, but
reduced the number of colony-forming units recovered from nodules. Further
analysis found that genes involved in the synthesis of indole-3-acetic acid
were upregulated. PvTRX1h downregulation also altered starch accumulation.
Based on these results, PvTRX1h likely alters the auxin signaling network to
determine bacterial colonization, nodule number, starch accumulation,
hormone levels, and cell proliferation in common bean.