Transcriptomic profiling of watermelon(Citrullus lanatus) provides insights into male flowers development

Watermelon(Citrullus lanatus(Thunb.) Matsum. & Nakai) is an important cucurbit crop grown worldwide. Watermelon fruit quality, fertility, and seed-setting rate are closely related to male flower development. In this study, the different developmental stages of flower buds of the watermelon cultivar ’Xinteda Zhengkang 9’ were distinguished by cytological observation, and transcriptome sequencing analysis was performed subsequently. Acetocarmine staining of anthers was performed and the longitudinal and transverse diameters of the unopened male flower buds were measured. Cytological observations of anthers at different developmental stages showed that the anther grew from the tetrad to the mature stage, and the longitudinal and transverse diameters of the flower buds increased. The length of the male flower buds also changed significantly during development. Transcriptome sequencing analysis at four periods, the tetrad(A group), mononuclear(B group), dikaryophase(C group), and mature stages(D group). A total of 16 288 differentially expressed genes(DEGs) were detected in the four stages, with the prolongation of developmental stages, the number of DEGs increased gradually in the comparison groups, there was 2 014, 3 259, 4 628, 1 490, 3 495 and 1 132 DEGs revealed in six comparison groups(A-vs.-B, A-vs.-C, A-vs.-D, B-vs.-C, B-vs.-D, and C-vs.-D), respectively. Gene Ontology(GO) and KEGG enrichment analysis showed that the DEGs were mainly enriched in cellular component and starch and sucrose metabolism, phenylpropanoid biosynthesis and pentose sugar, etc. Finally, we completely screened 59 DEGs in the six comparison groups, interestingly, we found one pollen-specific protein(Cla001608) that was significantly down-regulated(the value of log2 Fold Change up to 17.32), which indicated that it may play an important role in the development of male flowers. This work provides insight into the molecular basis of the developmental stages of male flowers in watermelon and may aid in dominant cross breeding.

THE EFFECT OF LOW TEMPERATURE ADVERSITY ON MALE FLOWERS AND POLLEN IN LARIX OLGENSIS

The electrie conductivity of pollen life-force and male flowers of Larix olgensis on condition of low temperature adversity has been respectively measured by means of fluorescent dying method and conductivity method in 1992 and 1994. The results indicate that:(1 ) If the same clonal pollen is treated at equal time at different low temperatures, there are significant differences in pollen life-force, the pollen life-force is the largest between O℃aild -3℃, in higher or lower temperature range, the pollen life-force will decrease. The measurement of electric conductivity of male flowers provcs that the low temperature of below -3℃ is the inain reason that the cell membrane is damaged and the pollen.life-force decreases. (2) The same clonal pollen life-force at the saine low temperature will gradually decrease with the increasing of frozen time. Its main reason is that suffocation and losing body fluid result in the damage of cell membrane, the measurement of electric conductivity of male flowers call prove that. (3) If pollen is treated with the same low temperature, the humidity will be the main factor of affecting pollen life-force. (4) There are significant differences in Larix olgensis's resistance against low temperature in its different growth stage, the male flower's resistance of near pollen spreading period is low. (5) The resistance is different within clones. (6) The resistance against low temperature of Larix call be incrcased by means of chemical treatment.

Growth and Development of Staminate Inflorescence and Anatomic Observation of Male Chestnut Flower

The growth and development of staminate inflorescence and anatomic structure of male chestnut flower were observed. Results showed that staminate in-florescence on the base of branch formed first, then upward successively. About 50 days were needed from the formation of staminate inflorescence on the base of branch to ful y develop the staminate inflorescence on the top of the branch. On the same staminate inflorescence, male flower clusters of the base formed first, then upward successively. About 20 days were needed from the formation of stami-nate inflorescence on the base of the male flower cluster to ful y develop the stami-nate inflorescence on the top of the branch. 5-7 male flowers forming a cluster, the flower number in a cluster was odd number usual y, and there was one on the top and each two paral el y arranged downward. The flower on the top came into bloom first, and then downward successively. The flowers paral el y arranged came into bloom at the same time. Sporangium of male flower of chestnut was monolocular. There were a large number of pol en grains in the sporangium. There were large differences between the development process of different sporangium in one male flower. Chestnut had larger quantity of male flowers and pol en and long period of pol ination compared with female flower. It is remained to be further studied whether it was necessary for anemophilous pol ination.

Genetic Analysis of the First Female Flower Node and the First Male Flower Node in Bitter Gourd

Exploring genetic mechanism of the first female flower node and the first male flower node in bitter gourd has practical significance for formulating breeding strategy. In this article, a cross was made between CN19-1 and Thai4-6, and the F2segregation population was also constructed through F1selfing. The genetic characteristics of the first female flower node and the first male flower node were analyzed by adopting the major gene plus polygene mixed genetic model. The data analysis results showed that the first female flower node and the first male flower node were continuous distribution in the F2segregation population. E-2 model was the most suitable model for the genetic analysis of the first female flower node and the first male flower node. The additive effect values of the 2 pairs of major genes controlling the first female flower node were 2.722 and 1.862 8 respectively, the dominant effect values were-2.721 6 and-0.171 8, respectively. The additive effect value of polygene was-0.839 2, and the dominant effect value of polygene was 2.225 4. The heritability of major genes and polygene were 83.73% and 1.54%, respectively. The additive effect values of the 2 pairs of major genes controlling the first male flower node were 17.746 9 and 3.972, respectively, the dominant effect values were 5.191 6 and-3.972, respectively. The additive effect value of polygene was-20.530 5, and the dominant effect value was-4.141 4. The heritability of major genes and polygene was 92.34% and 4.7%, respectively. This study could provide a theoretical basis for bitter gourd breeding.

Seed and Wasp Production in the Mutualism of Figs and Fig Wasps

Figs (Moracea: Ficus) and fig wasps (Hymenoptera: Chlocloids: Agaonideae) depend on each other to complete their reproduction. Monoecious fig species and their pollinating wasps are in conflict over the use of fig ovaries which can either produce one seed or one wasp. From observation on Ficus virens Ait., we showed that female flowers with outer layer of ovaries (near to the wall of syconium) had no significant difference from that with inner and interval layer of ovaries (near to the syconium cavity), in which most seeds and wasps were produced. This meant that fig tree provided the same potential resource for seed and wasps production. Observation indicated that there was usually only one foundress in syconium at female flower phase and no com- petition pollinators. Measurement of the style length of female flowers and the ovipositor of pollinators indicated that most ovaries could be reached by pollinator’s ovipositor. However, at the male flower phase, production of seeds was significantly more than that of wasps including non-pollinating wasps but there was no significant difference between seed and pollinating wasp production when without non-pollinating wasps produced. This result indicated that non-pollinating wasps competed ovaries not with seeds but with pollinating wasps for ovipositing. Bagged experiment showed that the sampling fig species was not self-sterile which was important for figs and wasps to survive bad season. Seed production in self-pollinated figs was not significantly different from total wasps in- cluding non-pollinating ones. This might be related with the weaker competition among wasps since bagged figs were not easy to reach by wasps from outside.