Sorghum stem aerenchyma formation is regulated by SbNAC_D during internode development

Abstract

Sorghum bicolor is a drought‐resilient C4 grass used for production of grain, forage, sugar, and biomass. Sorghum genotypes capable of accumulating high levels of stem sucrose have solid stems that contain low levels of aerenchyma. The D ‐locus on SBI 06 modulates the extent of aerenchyma formation in sorghum stems and leaf midribs. A QTL aligned with this locus was identified and fine‐mapped in populations derived from BT x623* IS 320c, BT x623*R07007, and BT x623*Standard broomcorn. Analysis of coding polymorphisms in the fine‐mapped D ‐locus showed that genotypes that accumulate low levels of aerenchyma encode a truncated NAC transcription factor (Sobic.006G147400, SbNAC_d1 ), whereas parental lines that accumulate higher levels of stem aerenchyma encode full‐length NAC TF s ( SbNAC‐D ). During vegetative stem development, aerenchyma levels are low in nonelongated stem internodes, internode growing zones, and nodes. Aerenchyma levels increase in recently elongated internodes starting at the top of the internode near the center of the stem. SbNAC_D was expressed at low levels in nonelongated internodes and internode growing zones and at higher levels in regions of stem internodes that form aerenchyma. SbXCP1 , a gene encoding a cysteine protease involved in programmed cell death, was induced in SbNAC_D genotypes in parallel with aerenchyma formation in sorghum stems but not in SbNAC_d1 genotypes. Several sweet sorghum genotypes encode the recessive SbNAC_d1 allele and have low levels of stem aerenchyma. Based on these results, we propose that SbNAC_D is the D ‐gene identified by Hilton (1916) and that allelic variation in SbNAC_D modulates the extent of aerenchyma formation in sorghum stems.

Transcriptional Regulation of Sorghum Stem Composition: Key Players Identified Through Co-expression Gene Network and Comparative Genomics Analyses

“…The second report concerns the NAC gene underlying the D locus (Sobic.006G147400), which control the stem juiciness. It is hypothesized that this gene modulates the proportion of aerenchyma in the middle part of the sorghum stems (Casto et al, 2018). From our perspective, this NAC gene belongs to the B clade and does not present evidence for a potential role in SCW deposition as we did not detect any strong co-regulation with SCW-related genes.…”

Distinct Expression and Methylation Patterns for Genes with Different Fates following a Single Whole-Genome Duplication in Flowering Plants

“…2019 ), the unique longevity of lotus seeds and their survival during K–pg boundary might have benefited from the duplication of these biosynthesis genes. Also, the well-developed aerenchyma in stem and rhizome of lotus might have benefited from the duplication of genes related to xylem and phloem ( Casto et al. 2018 ).…”

Maturity2, a novel regulator of flowering time in Sorghum bicolor, increases expression of SbPRR37 and SbCO in long days delaying flowering

“…Raw Ct values for each sample were normalized to C t values for the reference gene SbUBC (Sobic.001G526600). Reference gene stability was determined previously [43]. ΔΔC t values were calculated relative to the sample with the highest expression (lowest C t value).…”