AUTHOR=Tokumitsu Yusuke , Kozu Takuto , Yamatani Hiroshi , Ito Takeshi , Nakano Haruna , Hase Ayaka , Sasada Hiroki , Takada Yoshitake , Kaga Akito , Ishimoto Masao , Kusaba Makoto , Nakashima Taiken , Abe Jun , Yamada Tetsuya 

TITLE=Functional Divergence of G and Its Homologous Genes for Green Pigmentation in Soybean Seeds

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.796981

DOI=10.3389/fpls.2021.796981

ISSN=1664-462X

ABSTRACT=<p>The degradation of chlorophyll in mature soybean seeds is closely related to the development of their yellow color. In this study, we examined <italic>G</italic>, its homologue <italic>G-like</italic> (<italic>GL</italic>), and their mutant alleles and investigated the relationship between these genes and chlorophyll accumulation in the seed coats of mature seeds. Transient expression of G and GL proteins fused with green fluorescent protein revealed that both were localized in plastids. Overexpression of <italic>G</italic> resulted in the accumulation of chlorophyll in the seed coats and cotyledons of mature seeds, indicating that high expression levels of <italic>G</italic> result in chlorophyll accumulation that exceeds its metabolism in the seeds of yellow soybean. Analysis of near isogenic lines at the <italic>G</italic> locus demonstrated a significant difference in the chlorophyll content of the seed coats and cotyledons of mature seeds when <italic>G</italic> and mutant <italic>g</italic> alleles were expressed in the <italic>d<sub>1</sub>d<sub>2</sub></italic> stay-green genetic background, indicating that the G protein might repress the SGR-independent degradation of chlorophyll. We examined the distribution of mutant alleles at the <italic>G</italic> and <italic>GL</italic> loci among cultivated and wild soybean germplasm. The <italic>g</italic> allele was widely distributed in cultivated soybean germplasm, except for green seed coat soybean lines, all of which contained the <italic>G</italic> allele. The <italic>gl</italic> alleles were much fewer in number than the <italic>g</italic> alleles and were mainly distributed in the genetic resources of cultivated soybean from Japan. None of the landraces and breeding lines investigated in this study were observed to contain both the <italic>g</italic> and <italic>gl</italic> alleles. Therefore, in conclusion, the mutation of the <italic>G</italic> locus alone is essential for establishing yellow soybeans, which are major current soybean breeding lines.</p>