Short-term high temperature growth conditions during vegetative-to-reproductive phase transition irreversibly compromise cell wall invertase-mediated sucrose catalysis and microspore meiosis in grain sorghum ( Sorghum bicolor)

Abstract

Grain sorghum ( Sorghum bicolor) crop yield is significantly compromised by high temperature stress-induced male sterility, and is attributed to reduced cell wall invertase (CWI)-mediated sucrose hydrolysis in microspores and anthers leading to altered carbohydrate metabolism and starch deficiency in pollen ( Jain et al., 2007). Sorghum plants were grown under season-long ambient (30/20 °C day-time maximum/night-time minimum) or high temperature stress (HS, 36/26 °C) environments, or reciprocally transferred for 5–10 days between either temperature regimens through panicle and microspore developmental stages. Quantitative RT-PCR analyses for CWI gene SbIncw1, plasma membrane H +-ATPase ( Mha1) and sugar transporter proteins ( OsSUT3 and OsMST7 homologs in sorghum), starch deficiency and pollen sterility data are presented to confirm HS-sensitivity of pre- and post-meiotic stages of sorghum microsporogenesis. Heat stress-induced reduction in Incw transcriptional activity during microspore meiosis was irreversible despite return of optimal growth temperature conditions through further reproductive development.