Unmasking the mysteries of catkin floral Initiation in Carya illinoinensis through RNA-Seq analysis

Authors: RHEIN, H - New Mexico State University; SCHMUTZ, J - Hudsonalpha Institute For Biotechnology; GRIMWOOD, J - Hudsonalpha Institute For Biotechnology; JENKINS, J - Hudsonalpha Institute For Biotechnology; HEEREMA, R - New Mexico State University; Grauke, Larry; RANDALL, JENNIFER - New Mexico State University

Submitted to: American Society of Plant Biologists
Publication Type: Abstract Only
Publication Acceptance Date: 8/2/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Carya illinoinensis (pecan) is native to North America and belongs to the Juglandaceae family. Pecan nuts contain high and healthful levels of mono-unsaturated fats and antioxidants and are currently being produced in several areas throughout the world. Carya illinoinensis is heterodichogamous with genotypes that are either protandrous or protogynous. A major constraint in pecan breeding programs is the extensive juvenile phase which typically lasts 8-15 years. To date, the transition from vegetative to reproductive phase and the genetic mechanism of flower initiation in pecan is unknown. Year to year fluctuations in pecan nut numbers per tree (alternate bearing) is a constraint for commercial pecan production and is thought to occur as a function of variation in floral initiation. RNA-Seq studies followed by qRT-PCR was used to examine the gene expression involved in the floral initiation of protandrous and protogynous genotypes. In this study, 52 RNA libraries were constructed from bud tissues at different time points through the growing season of a protandrous ('Western') and protogynous ('Wichita') genotype. The data obtained from this analysis suggests that floral initiation may occur in a two-step pattern. The first step occurs in the buds the summer prior to flower bloom with a second decision step that occurs in the beginning of Spring prior to bloom. This study evaluated the expression levels of the different copies of the known flowering genes to determine the active form of the genes involved in the initiation of flowering. Differential gene expression between protandrous ('Western') and protogynous ('Wichita') cultivars was also evaluated to differentiate the genes involved in formation of catkin and pistillate flowers. These data show significant differences in expression of known flowering genes between protandrous and protogynous genotypes.