Interaction between induced and natural variation atoil yellow1delays reproductive maturity in maize

Abstract

24We previously demonstrated that maize (Zea mays) locus very oil yellow1 (vey1) encodes a 25 putative cis-regulatory expression polymorphism at the magnesium chelatase subunit I gene (aka 26 oil yellow1) that strongly modifies the chlorophyll content of the semi-dominant Oy1-N1989 27 mutants. The vey1 allele of Mo17 inbred line reduces chlorophyll content in the mutants leading 28 to reduced photosynthetic output. Oy1-N1989 mutants in B73 reached reproductive maturity four 29 days later than wild-type siblings. Enhancement of Oy1-N1989 by the Mo17 allele at the vey1 QTL 30 delayed maturity further, resulting in detection of a flowering time QTL in two bi-parental 31 mapping populations crossed to Oy1-N1989. The near isogenic lines of B73 harboring the vey1 32 allele from Mo17 delayed flowering of Oy1-N1989 mutants by twelve days. Just as previously 33 observed for chlorophyll content, vey1 had no effect on reproductive maturity in the absence of 34 the Oy1-N1989 allele. Loss of chlorophyll biosynthesis in Oy1-N1989 mutants and enhancement 35 by vey1 reduced CO2 assimilation. We attempted to separate the effects of photosynthesis on the 36 induction of flowering from a possible impact of chlorophyll metabolites and retrograde signaling 37 by manually reducing leaf area. Removal of leaves, independent of the Oy1-N1989 mutant, 38 delayed flowering but surprisingly reduced chlorophyll contents of emerging leaves. Thus, 39 defoliation did not completely separate the identity of the signal(s) that regulates flowering time 40 from changes in chlorophyll content in the foliage. These findings illustrate the necessity to explore 41 the linkage between metabolism and the mechanisms that connect it to flowering time regulation. 42 43

Variation in maize chlorophyll biosynthesis alters plant architecture

“…The highly heritable vey1 QTL is a major modifier of chlorophyll contents in heterozygous Oy1-N1989/+ mutants but had no effect on chlorophyll accumulation in wildtype plants from either B73 x Mo17 biparental mapping populations or a maize association panel (Khangura et al 2019a). The vey1 alleles are detectable as a cis-acting eQTL and generate allele-specific expression at oy1 (Li et al 2013(Li et al , 2018Waters et al 2017;Khangura et al 2019aKhangura et al , 2019b. These expression level differences at oy1 are visible at the mRNA level in both mutants and wildtypes, but the impact on chlorophyll content was only visible in the presence of the Oy1-N1989 allele (Khangura et al 2019a).…”

“…One way to manipulate photosynthetic activity and energy resources in plants is by altering chlorophyll biosynthesis (Walker et al 2017;Khangura et al 2019a). Magnesium chelatase (MgChl) is a hetero-oligomeric enzyme complex that catalyzes the first committed step of chlorophyll biosynthesis by conversion of protoporphyrin IX (PPIX) into magnesium-PPIX (Walker and Weinstein 1991;Gibson et al 1995).…”

“…This gene received its name because weak hypomorphic alleles result in a light green to yellow color reminiscent of vegetable oil (Eyster 1933;Sawers et al 2006). We previously demonstrated that the semi-dominant Oy1-N1989 mutant was strongly modified by a QTL called very oil yellow1 (vey1) that is likely encoded by cis-acting regulatory polymorphisms at oy1 itself (Khangura et al 2019a). The highly heritable vey1 QTL is a major modifier of chlorophyll contents in heterozygous Oy1-N1989/+ mutants but had no effect on chlorophyll accumulation in wildtype plants from either B73 x Mo17 biparental mapping populations or a maize association panel (Khangura et al 2019a).…”

“…We previously demonstrated that the semi-dominant Oy1-N1989 mutant was strongly modified by a QTL called very oil yellow1 (vey1) that is likely encoded by cis-acting regulatory polymorphisms at oy1 itself (Khangura et al 2019a). The highly heritable vey1 QTL is a major modifier of chlorophyll contents in heterozygous Oy1-N1989/+ mutants but had no effect on chlorophyll accumulation in wildtype plants from either B73 x Mo17 biparental mapping populations or a maize association panel (Khangura et al 2019a). The vey1 alleles are detectable as a cis-acting eQTL and generate allele-specific expression at oy1 (Li et al 2013(Li et al , 2018Waters et al 2017;Khangura et al 2019aKhangura et al , 2019b.…”

“…The vey1 alleles are detectable as a cis-acting eQTL and generate allele-specific expression at oy1 (Li et al 2013(Li et al , 2018Waters et al 2017;Khangura et al 2019aKhangura et al , 2019b. These expression level differences at oy1 are visible at the mRNA level in both mutants and wildtypes, but the impact on chlorophyll content was only visible in the presence of the Oy1-N1989 allele (Khangura et al 2019a). This allelic interaction indicates the value of using mutants to uncover hidden genetic variation in maize.…”