ARS | Publication request: 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

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 28, 2009
Publication Date: January 1, 2010
Citation: Jain, M., Chourey, P.S., Boote, K.J., Allen Jr, L.H. 2010. 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. Journal of Plant Physiology. 167:578-582.

Interpretive Summary: Previous cooperative efforts among scientists from USDA ARS, CMAVE and the University of Florida, Gainesville, led to show that sugar – starch pathway in developing pollen is most susceptible to break down under high temperature stress in maize and sorghum. A continuation of this coop effort has now led to this report that identifies certain specific genes in this pathway, most notably a pollen-specific cell wall invertase that is irreversibly down-regulated in plants exposed to high temperature for short or long term duration. Further characterization and eventual incorporation of such ‘heat-tolerant’ genes will provide superior germplasm that is expected to be better adapted to growth conditions associated with global warming.

Technical Abstract: Grain sorghum (Sorghum bicolor L. Moench) 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.