Are retinal and retinal-binding proteins involved in stomatal response to blue light?

Light sensitivity of shoot hydraulic conductance in five temperate deciduous tree species

The light sensitivity of the shoot hydraulic conductance in five temperate deciduous tree species was measured using two methods to clarify the role of light sensitivity and the suitability of the methods used to study it. The light sensitivity measured using a method that included an interruption of ≤10min in shoot light acclimation did not differ from that measured using a method with continuous illumination. The 'noncontinuous light' methods are suitable for measuring hydraulic conductance and its light response. Light sensitivity correlated with other leaf water traits as follows: positively with the ion-mediated increase in xylem hydraulic conductance; a relative decrease in the hydraulic conductance of the laminae in response to HgCl2; a relative change in stomatal conductance in response to changes in PAR intensity or atmospheric CO2 concentration, or to a decrease in air humidity or leaf water potential; and with instantaneous water use efficiency. The traits correlated negatively with shoot hydraulic conductance, stomatal conductance and relative increases in stomatal conductance in response to increases in leaf water potential. We suggest that high light sensitivity should be considered as one of the characteristics of conservative water use in trees. Low blue light increased shoot hydraulic conductance to a similar extent to moderate white light and twice as much as moderate red light. Blue light perception is important in the light sensitivity mechanism.

Transcript profiling in Vitis riparia during chilling requirement fulfillment reveals coordination of gene expression patterns with optimized bud break

Endodormant grapevine buds require a period of chilling before they break and begin to grow. Custom Vitis bud cDNA microarrays (9,216 features) were used to examine gene expression patterns in overwintering Vitis riparia buds during 2,000 h of 4 degrees C chilling. Three-node cuttings collected concurrently with buds were monitored to determine dormancy status. Chilling requirement was fulfilled after 1,500 h of chilling; however, 2,000 h of chilling significantly increased the rate of bud break. Microarray analysis identified 1,469 significantly differentially expressed (p value < 0.05) array features when 1,000, 1,500, and 2,000 h of chilling were compared to 500 h of chilling. Functional classification revealed that the majority of genes were involved in metabolism, cell defense/stress response, and genetic information processing. The number of significantly differentially expressed genes increased with chilling hour accumulation. The expression of a group of 130 genes constantly decreased during the chilling period. Up-regulated genes were not detected until the later stages of chilling accumulation. Hierarchical clustering of non-redundant expressed sequence tags revealed inhibition of genes involved in carbohydrate and energy metabolism and activation of genes involved in signaling and cell growth. Clusters with expression patterns associated with increased chilling and bud break were identified, indicating several candidate genes that may serve as indicators of bud chilling requirement fulfillment.

Cryptochrome 2 is involved in betacyanin decomposition induced by blue light in Suaeda salsa

Seeds of the halophyte Suaeda salsa (L.) Pall. were cultured in 24 h dark and 14 h blue light / 10 h dark to examine the role of blue light and the blue-light-absorbing photoreceptor cryptochrome 2 (CRY2) in betacyanin accumulation, hypocotyl elongation and cotyledon opening in S. salsa seedlings. Darkness significantly promoted betacyanin accumulation and hypocotyl elongation but inhibited cotyledon opening. Blue light suppressed betacyanin accumulation and hypocotyl elongation but stimulated cotyledon opening. Betacyanin in S. salsa seedlings decomposed with time in blue light. Western blot analysis showed that CRY2 protein accumulated both in hypocotyls and cotyledons of S. salsa seedlings grown in dark, but degraded with time in blue light, which was paralleled by a decrease of tyrosine hydroxylation activity of tyrosinase, a key enzyme involved in the betalain biosynthesis pathway. These results suggest that CRY2 protein mediates betacyanin decomposition via inactivation of tyrosinase in S. salsa seedlings, and the blue-light-dependent degradation of CRY2 protein is crucial to its function.