Abstract

AG1 Enhances Anaerobic Germination Tolerance, A Key Trait to Boost Direct-Seeded Rice

Endang Septiningsih, Assistant Professor, Texas A&M University

Global socioeconomic developments are driving the introduction of direct-seeded rice (DSR) across many regions in rice producing countries. Anaerobic germination (AG) tolerance, which enables uniform germination and seedling establishment under submergence, is a key trait for the development of tropical DSR varieties. A major QTL, qAG-9-2, was identified from a Myanmar landrace, Khao Hlan On, a donor for high tolerance of AG. This QTL was fine-mapped to a ~50 kb region on chromosome 9 that contains four genes and one transposable element in the Nipponbare reference genome. Here, we identify AG1 as the genetic determinant in qAG-9-2. Of the genes within the fine-mapped region, only transcripts of AG1 were detectable in germinating tissues of a qAG-9-2-containing near-isogenic line which displayed AG tolerance as monitored by increased survival under submergence. Analysis of the over-expressed and loss-of-function AG1 transgenic lines confirmed this finding.  AG1 expression was found in young sink tissues, whereas it was absent in photosynthetic leaves and the endosperm. We proposed that AG1 activity may increase sink strength in proliferating heterotrophic tissues by indicating low sugar availability, thus enhancing starch mobilization to drive growth kinetics of the germinating embryo and elongating coleoptile, which consequently enhances AG tolerance.