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NAC transcription factor is a new-found and multifunctional transcription factor in plants. The purpose of the paper is to study the relative expression trends of BnNAC transcription factor gene under cold (4°C), salinity (200 mM NaCl) and abscisic acid (ABA) (100 μM) stress in Brassica napus. The functional region of BnNAC gene was cloned through the homologous cloning method. The sequences of nucleic acid and amino acid were analyzed using BLAST and DNAMAN software. Relative expression trends of BnNAC gene were detected by applying real-time relative quantification PCR (RT-qPCR) under cold, salinity and ABA treatment. A 440 bp BnNAC gene segment was acquired in Brassica napus. BnNAC gene expressions of Brassica napus seedlings were induced under cold, salinity and ABA treatment conditions. The results of RT-qPCR analysis revealed that, under salinity, cold and ABA conditions, the relative expression of BnNAC gene increases with time, reaches the peak at 24h, 3h, 12h respectively and then decreases. Our research showed that BnNAC plays a positive role in salinity, cold and ABA stress response.

Deterioration of peach fruit quality because of split-pit formation had bad influence on market (1). Though many studies have mentioned the mechanism of split-pit formation, further studied are still needed to uncover the development mechanism of endocarp cell during pit hardening process, especially the Programmed cell death (PCD) process of peach endocarp cell. Here, the development of the peach endocarp cell from the two Chinese peach varieties "Jingyu" and "Okubo" was detailedly studied to understand the PCD of endocarp cell during the lignin formation process. According to our morphology observation using transmission electron microscopy, the PCD process of the endocarp cell, characterized by vacuolar enlargement, might have been initiated as early as eight days after full athesis (maybe even more earlier), which is earlier than that of the split-pit formation process. In our studies, almost all the endocarp cell organelles were found to degenerate at forty days after full athesis, when thickening of the endocarp cell wall was also observed. Furthermore, the involvement of hydrolytic enzymes, in particular proteases and nucleases, in the autolytic process of PCD of peach endocarp cells was quantitatively analyzed during pit hardening process. The peach endocarp protein was found to be rapidly degraded by newly expressed proteases since 35 days after full athesis. Elevation of nuclease activities was found to be also coupled with PCD of peach endocarp cells. Furthermore, DNA degradation was found to happen earlier than RNA degradation and hydrolyzing of endocarp soluble protein during the peach pit hardening process.

Few studies were mentioned to illustrate the role of plant hormones-IAA and ethylene in split-pit formation. Here, a random sample of 100 developing fruits from 7-year-old early maturing nectarines (Prunus persica L. Batsch cv. Ruiguang 5) was used as test material. The shape index and growth index of the sampled nectarines was comparatively analyzed to show the relation between fruit un-uniform growth and their split-pit formation. The split-pit fruits were found to have a higher degree of un-uniform growth than that of the normal fruits, which were demonstrated by higher ratio of transverse diameter/lateral diameter and bigger difference between the flesh thickness of the two sides in the middle part of the fruits (along the line of the transverse diameter) about twelve weeks after full anthesis (p < 0.05). Subsequently, a higher degree of unbalanced distribution of IAA and especially ethylene was observed in the split-pit fruits compared to the normal fruits, which may correlate with un-balanced expansion of the nectarines flesh. Higher concentration of IAA and especially ethylene was found in the middle part of the split-pit fruits than those in the sutures, while those in the normal fruits were not significant. Furthermore, the caliosity was specifically observed in the internal surface of the split-pit nectarines endo carp as early as four weeks after full anthesis, but not in the normal nectarines. The occurrence of caliosit in the endo carp may be an early signal of spilt-pit.