Proline Content of the Anthers and Pollen of Heat‐Tolerant and Heat‐Sensitive Cowpea Subjected to Different Temperatures

Abstract

High temperatures cause reductions in grain yield of cowpea [(Vigna unguiculata (L.) Walp.] that are associated with low pollen viability and pod set. Preliminary controlled environment studies showed differences in proline accumulation in anthers and pollen of heat‐tolerant and heat‐sensitive genotypes under hot and optimal temperatures, but insufficient tissue was available to establish if the differences were significant. The objective was to determine whether heat injury under field conditions is associated with specific patterns of proline accumulation in leaves and reproductive tissue using heat‐sensitive an heat‐tolerant cowpea genotypes. Under moderate and hot temperatures, proline was the most abundant free amino acid in the anthers of both heat‐sensitive and heat‐tolerant cowpea genotypes. No differences in leaf proline concentrations were observed. Under hot conditions, proline levels in anthers decreased faster as pollen matured in heat‐tolerant genotypes as compared with heat‐sensitive genotypes. At pollen maturity, heat‐sensitive genotypes contained more proline in anthers and had lower levels in pollen than the heat‐tolerant genotypes under hot conditions but similar levels under more optimal temperatures. The results suggest that heat injury during floral development of sensitive cowpea genotypes may be due to inhibition of proline translocation from anther walls to pollen.

Osmoregulation of a Pyrroline-5-Carboxylate Reductase Gene in Arabidopsis thaliana

“…7A) and free Pro accumulates more in flowers than in leaves of flowering plants (5.2% of the total free amino acid pool versus 0.5%) (N. Verbruggen, unpublished data). These observations support the idea that Pro is likely to play a role in flower development, as suggested by Vansuyt et al (1979), Mutters et al (1989), and Walton et al (1991). Furthennore, AT-P5CI transcripts are very abundant in ripening seeds, which have to face drought stress.…”

Proline Metabolism and Its Implications for Plant-Environment Interaction

“…Proline content is high in reproductive tissues (Mutters et al, 1989;Chiang and Dandekar, 1995;Schwacke et al, 1999;Matsui et al, 2008;Mattioli et al, 2009). P5CS1 and P5CR were also found to be highly expressed in reproductive tissues (Verbruggen et al, 1993;Savoure et al, 1995).…”

Pollen Development at High Temperature: From Acclimation to Collapse

“…Pro acts as a compatible solute in osmoprotection and accumulates in response to different abiotic stresses (Krasensky and Jonak, 2012). Pro is a key factor for pollen viability (Lansac et al, 1996), and in several species, levels decrease in pollen under high temperature regimes that disturb pollen development (Mutters et al, 1989;Tang et al, 2008). Interestingly, the expression of Pro transporter 1 mRNA was reduced under these conditions.…”