Effects of Heterologously Overexpressing PIP5K-Family Genes in Arabidopsis on Inflorescence Development

Castor is one of the top 10 oil crops in the world and has extremely valuable uses. Castor inflorescences directly affect yield, so the study of inflorescence development is very important in increasing castor yield. Our previous studies have shown that the PIP5K gene family (PIP5Ks) is associated with inflorescence development. In this study, to determine the function of each PIP5K gene in castor, a female Lm-type castor line, aLmAB2, was used to determine the relative expression levels of the PIP5Ks in castor inflorescences. Six PIP5K genes were heterologously overexpressed in Arabidopsis thaliana, the relative expression of each gene and the effect on plants was determined in A. thaliana, and the relationships among the PIP5Ks in castor were inferred. The expression levels of the PIP5Ks in the female Lm-type castor line aLmAB2 were analyzed. The relative expression levels of the PIP5K9 and PIP5K11 genes were high (p < 0.05) in isofemale inflorescences, and those of PIP5K1, PIP5K2, PIP5K6, and PIP5K8 were high (p < 0.05) in female inflorescences but low (p < 0.05) in bisexual inflorescences. The PIP5Ks were heterologously overexpressed in A. thaliana, and T3-generation plants with stable genetic resistance, i.e., AT-PIP5K(+) plants (AT-PIP5K1(+), AT-PIP5K2(+), AT-PIP5K6(+), AT-PIP5K8(+), AT-PIP5K9(+), and AT-PIP5K11(+) plants), were obtained. Biological tests of the AT-PIP5K(+) plants showed that the growth of the main stem was significantly delayed in AT-PIP5K(+) plants compared with Columbia wild-type (WT) A. thaliana plants; the PIP5K1 and PIP5K2 genes promoted lateral stem growth and flower and silique development; and the PIP5K6, PIP5K8, PIP5K9 and PIP5K11 genes inhibited lateral stem growth and flower and silique development. The correlations among PIP5Ks in castor suggest that there may be a synergistic relationship among PIP5K1, PIP5K2, and PIP5K6 in castor inflorescences, and PIP5K8, PIP5K9, and PIP5K11 are complementary to the other three genes.