Most photorespiratory genes are preferentially expressed in the bundle sheath cells of the C₄grassSorghum bicolor

Abstract

HighlightPhotorespiratory genes are expressed tissue-specific in the leaves of the C4 grass Sorghum bicolor. Most but not all of them are confined to the bundle sheath cells.

The role of alanine and aspartate aminotransferases in C4 photosynthesis

“…() for G. gynandra mesophyll and bundle sheath tissue; in Doring et al . () for Sorghum bicolor total leaf tissue. The graphs show the transcript abundances in transcript per million (tpm) as presented in the Supplements of Denton et al .…”

“…The Ala and Asp ATs and MDH patterns were determined from transcriptome analysis published in Eisenhut et al (2017) for A. thaliana wild type ambient CO 2 ; in Kulahoglu et al (2014) for Tarenaya hassleriana and Gynandropsis gynandra, mature leaf; in Wang et al (2014a) for Orysa sativa, leaf sections 7, 8, 9 and 10; in Chang et al (2012) for Zea mays mesophyll and bundles sheath tissue; in Denton et al (2017) for Z. mays mesophyll and bundle sheath tissue in a leaf gradient; in for Panicum virgatum mesophyll and bundle sheath tissue; in John et al (2014) for Setaria viridis mesophyll and bundle sheath tissue; in Aubry et al (2014) for G. gynandra mesophyll and bundle sheath tissue; in Doring et al (2016) for Sorghum bicolor total leaf tissue. The graphs show the transcript abundances in transcript per million (tpm) as presented in the Supplements of Denton et al (2017) for Z. mays, P. virgatum and S. viridis.…”

Understanding metabolite transport and metabolism in C4 plants through RNA-seq

“…The module requires the action of pyrophosphorylase (PPase) and AMP kinase (AMK) to drive the reaction and funnel PP and AMP back into metabolism as phosphate and ADP [23]. The module is only 80% specific to the mesophyll in Zea mays [24 ] and Sorghum bicolor [25] based on transcript abundances (Table 1, data extracted from [24 ]), but also controlled at the posttranscriptional level [26]. Two prototypes of the module are currently known (Figure 1b and c).…”

“…The C 4 Andropogonae such as sorghum or maize are known to exchange pyruvate for protons directly [27] and consequently, neither BASS2 nor NHD can be detected as highly abundant in maize (Table 1) [25]. Instead of the conjunct action of BASS and NHD, the Andropogonae have an alternative transport protein in mesophyll chloroplasts which, to date, has not been characterized at the molecular level ( Figure 1c, Table 1).…”

“…The dicarboxylate transporter DiT2 (alternate name DCT) was considered a candidate transporter for malate in maize [35], however, the Flaveria trinervia DiT2 is unable to catalyze the reaction based on in vitro analysis of the transport substrates [36]. DiT2 is moderately upregulated in conjunction with NADP-ME [6][7][8] and DiT2 is strongly expressed in maize bundle sheath cells (Table 1) and S. bicolor bundle sheath cells [25]. Mutant analysis of maize showed symptoms consistent with a role in malate import in the C 4 cycle [37 ] raising the question whether the original assay was unsuitable for detecting the exchange [36] or whether Flaveria and maize may use different transporters (Figure 1d).…”