Inter-varieties variation of sugar metabolism that inhibit
photosynthesis: hexokinase-dependent stomatal and non-stomatal behaviors
Abstract
The generation of sugar from photosynthesis and its utilization by sugar
metabolism jointly determine the leaf sugar status, which conversely
represses photosynthesis. The objective of this study was to investigate
the effect of leaf sugar metabolism on photosynthesis in two contrasting
grape (Vitis vinifera L.) genotypes, Riesling (RI, high level hexose)
and Petit Manseng (PM, low level hexose). The total hexose and glucose
contents of the RI leaves were significantly higher than those of PM
relative to the low level of fructose. The activity of cell wall
invertase for sucrose hydrolysis and the abundances of VvCWINV, VvHT4,
VvTMT1, VvFK1 and VvFK1 transcripts were higher in RI leaves. The
abundance of hexokinase transcript (VvHXK2) for signal sensing was also
higher, while VvHXK1 was lower for glucose phosphorylation. The net
photosynthetic rate, stomatal conductance, transpiration rate and
chlorophyll content of RI leaves were lower than those of PM and
negatively correlated with the hexose and glucose contents and the
VvHXK2, VvCWINV, VvHT4, and VvTMT1 transcript levels. These results
suggest that variation in sugar metabolism by inter-varieties alters the
cellular sugar status, which is important for regulating photosynthesis.
This study provides insights on improving the photosynthesis of
cultivars by metabolic modification for breeding.