AUTHOR=Xu Yiteng , Wang Hongfeng , Lu Zhichao , Wen Lizhu , Gu Zhiqun , Zhang Xue , Yu Guangle , Wang Hailong , Zhou Chuanen , Han Lu 

TITLE=Developmental Analysis of the GATA Factor HANABA TARANU Mutants in Medicago truncatula Reveals Their Roles in Nodule Formation

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.616776

DOI=10.3389/fpls.2021.616776

ISSN=1664-462X

ABSTRACT=<p>Formation of nodules on legume roots results from symbiosis with rhizobial bacteria. Here, we identified two GATA transcription factors, <italic>MtHAN1</italic> and <italic>MtHAN2</italic>, in <italic>Medicago truncatula</italic>, which are the homologs of <italic>HANABA TARANU</italic> (<italic>HAN</italic>) and <italic>HANABA TARANU LIKE</italic> in <italic>Arabidopsis thaliana</italic>. Our analysis revealed that <italic>MtHAN1</italic> and <italic>MtHAN2</italic> are expressed in roots and shoots including the root tip and nodule apex. We further show that <italic>MtHAN1</italic> and <italic>MtHAN2</italic> localize to the nucleus where they interact and that single and double loss-of-function mutants of <italic>MtHAN1</italic> and <italic>MtHAN2</italic> did not show any obvious phenotype in flower development, suggesting their role is different than their closest Arabidopsis homologues. Investigation of their symbiotic phenotypes revealed that the <italic>mthan1 mthan2</italic> double mutant develop twice as many nodules as wild type, revealing a novel biological role for GATA transcription factors. We found that <italic>HAN1/2</italic> transcript levels respond to nitrate treatment like their Arabidopsis counterparts. Global gene transcriptional analysis by RNA sequencing revealed different expression genes enriched for several pathways important for nodule development including flavonoid biosynthesis and phytohormones. In addition, further studies suggest that <italic>MtHAN1</italic> and <italic>MtHAN2</italic> are required for the expression of several <italic>nodule-specific cysteine-rich</italic> genes, which they may activate directly, and many peptidase and peptidase inhibitor genes. This work expands our knowledge of the functions of <italic>MtHANs</italic> in plants by revealing an unexpected role in legume nodulation.</p>