Integrated Genome-Scale Analysis Identifies Novel Genes and Networks Underlying Senescence in Maize

Abstract

Premature senescence in annual crops reduces yield, while delayed senescence, termed stay-green, imposes positive and negative impacts on yield and nutrition quality. Despite its importance, scant information is available on the genetic architecture of senescence in maize (Zea mays) and other cereals. We combined a systematic characterization of natural diversity for senescence in maize and coexpression networks derived from transcriptome analysis of normally senescing and stay-green lines. Sixty-four candidate genes were identified by genome-wide association study (GWAS), and 14 of these genes are supported by additional evidence for involvement in senescence-related processes including proteolysis, sugar transport and signaling, and sink activity. Eight of the GWAS candidates, independently supported by a coexpression network underlying stay-green, include a trehalose-6-phosphate synthase, a NAC transcription factor, and two xylan biosynthetic enzymes. Source-sink communication and the activity of cell walls as a secondary sink emerge as key determinants of staygreen. Mutant analysis supports the role of a candidate encoding Cys protease in stay-green in Arabidopsis (Arabidopsis thaliana), and analysis of natural alleles suggests a similar role in maize. This study provides a foundation for enhanced understanding and manipulation of senescence for increasing carbon yield, nutritional quality, and stress tolerance of maize and other cereals.

Interaction Between Induced and Natural Variation at oil yellow1 Delays Reproductive Maturity in Maize

“…Leaf senescence is suppressed by Oy1-N1989 in a vey1-dependent manner Leaf senescence can be induced in maize by sucrose accumulation in the leaves. This can be accomplished genetically by disrupting sucrose transport (Braun et al 2006;Baker and Braun 2008;Slewinski et al 2009) or by preventing the maize ears from acting as a sink (Allison and Weinmann 1970;Sekhon et al 2012Sekhon et al , 2019. Previous studies have shown that maize leaf senescence caused by pollination prevention or ear removal before pollination is genotype-dependent (Ceppi et al 1987).…”

“…Accumulation of sugars in the leaves due to sink disruption has been proposed to induce leaf senescence in a variety of angiosperms, including maize and Arabidopsis (Allison and Weinmann 1970;Ceppi et al 1987;Pourtau et al 2006;Sekhon et al 2012Sekhon et al , 2019. In maize, leaf senescence is triggered when pollination is prevented and sucrose accumulates in leaves due to the lack of the sink activity Figure 9 The effect of vey1 on senescence induced by pollination prevention.…”

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

“…Lower levels of 443 sugars and starch in the Oy1-N1989/+ mutant heterozygotes enhanced by a vey1 Mo17 allele is 444 consistent with the observation of lower chlorophyll levels and photosynthetic rates in these 445 genotypes compared to the suppressed mutant NILs. 446 Weinmann 1970; Sekhon et al 2012Sekhon et al , 2019. Previous studies have shown that maize leaf 471 senescence caused by pollination prevention or ear removal before pollination is genotype-472 dependent (Ceppi et al 1987).…”

Senescence: The Genetics behind Stay-Green Corn

“…Candidate genes are active in sugar signaling and transport between source and sink tissues. (Reprinted from Sekhon et al [2019], Figure 8.) [OPEN] Articles can be viewed without a subscription.…”

“…Knockout of mir3 in Arabidopsis delayed leaf senescence, suggesting the role of this gene in senescence in both monocots and dicots. Sekhon et al (2019) also explained the role of sugar partitioning and sugar signaling in senescence by placing nine candidate genes in a model (see figure). The candidate genes represent diverse processes, including sugar-mediated signaling (trps13), transport (ZmSWEET1b and ZmMST4), and control of sugar uptake (dek10).…”